Handbook of clinical drug data - part 5 ppt

PO for OCD 20 mg/day initially; maintenance dosage is 40 mg/day to a maximum of 60 mg/day, preferably as a single dose in the morning or evening.. Initiate therapy with divided doses unt

Pharmacology Nefazodone is a postsynaptic serotonin 5-HT2Aantagonist andpresynaptic serotonin reuptake inhibitor These two serotonergic effects make itdifferent from SSRIs and TCAs.153–156(See Antidepressants Comparison Chart.)

Administration and Adult Dosage PO for depression 100 mg bid initially (50 mg

bid in the elderly), increasing q 4–7 days to the effective dosage range of 150–

300 mg bid After initial dosage titration, once-daily bedtime administration ispreferred to minimize daytime sedation.157

Dosage Forms Tab 50, 100, 150, 200, 250 mg.

Pharmacokinetics Nefazodone has an oral bioavailability of about 20%

Single-dose studies in the elderly have shown a 100% larger AUC; with multiple Single-doses,the AUC differences decreased to 10–20% above those in younger populations It

is >99% protein bound and extensively metabolized, with a dose-dependent nation half-life of about 1–2.3 hr in young patients, modestly prolonged in theelderly, and 2–3 times longer in hepatic disease The major active metabolite,hydroxynefazodone, has a half-life of 1.2–1.6 hr in young and elderly patients,increasing to 2–4 hr with hepatic disease Renal impairment does not markedlyaffect nefazodone pharmacokinetics

elimi-Adverse Reactions Although chemically similar to trazodone, it causes less

se-dation and orthostatic hypotension, and its lower -adrenergic blockade makespriapism much less likely (no cases reported) Frequent adverse effects include se-dation, dry mouth, nausea, and dizziness Unlike SSRIs, nefazodone’s effects onsexual function, agitation, tremor, insomnia, and weight are no different fromplacebo

Drug Interactions Nefazodone is a potent inhibitor of the CYP3A4 isoenzyme

and a weak inhibitor of the CYP2D6 isoenzyme Drug interactions of particularconcern include the triazolobenzodiazepines (ie, alprazolam, triazolam, midazo-lam) A 1- to 2-week washout period is recommended when converting a patient

to or from a MAOI and nefazodone

Pharmacology Paroxetine is a highly selective and potent inhibitor of serotonin

reuptake (an SSRI) similar to fluoxetine.126,158–164(See Antidepressants

Compari-son Chart.)

Administration and Adult Dosage PO for depression 20 mg/day; a few patients

require 30–50 mg/day for full efficacy PO for social anxiety disorder and panic

disorder 10 mg/day initially; usual maintenance dosage is 20–60 mg/day PO for OCD 20 mg/day initially; maintenance dosage is 40 mg/day to a maximum of

60 mg/day, preferably as a single dose in the morning or evening The startingdosage for all uses in elderly patients and those with marked renal or hepatic im-pairment is 10 mg/day For the elderly or those with severe renal or hepatic im-pairment, the maximum dosage is 40 mg/day

Dosage Forms Tab 10, 20, 30, 40 mg; SR Tab 12.5, 25 mg; Susp 2 mg/mL.

Pharmacokinetics Paroxetine is completely orally bioavailable; protein binding

is 93–95% Unlike fluoxetine, paroxetine is metabolized to inactive metabolitesand has an elimination half-life of 24 hr

Adverse Reactions Paroxetine causes the typical SSRI adverse effects of nausea,

sexual dysfunction, and headache but is more likely to cause sedation than nia and can cause more delay of orgasm or ejaculation and more impotence thanother SSRIs.165Like the other SSRIs, it is much safer in overdose than TCAs

insom-Drug Interactions Paroxetine is a potent inhibitor of CYP2D6, so most other

an-tidepressants, antipsychotics, -blockers, and type Ic antiarrhythmics can have creased serum levels and adverse effects when paroxetine is combined with thesedrugs Do not use paroxetine within 14 days of using an MAOI

in-Pharmacology Reboxetine is the first in a new class of selective norepinephrine

reuptake inhibitors with no affinity for serotonin or dopamine reuptake sites It hasnegligible affinity for muscarinic, histaminic, or adrenergic receptors This nor-adrenergic mechanism for antidepressant efficacy is similar to TCAs such as des-ipramine without the potential for appreciable adverse anticholinergic, cardiovas-cular, and sedative effects It has efficacy for major depression equal to fluoxetineand desipramine.166,167(See Antidepressants Comparison Chart.)

Administration and Adult Dosage PO for depression 8–10 mg/day given bid,

4–6 mg/day given bid in the elderly

Dosage Forms Tab 4 mg (investigational).

Pharmacokinetics Reboxetine is rapidly absorbed Metabolism occurs through

three oxidative pathways: hydroxylation, dealkylation, and oxidation TheCYP450 isoenzymes responsible for metabolism have not been identified, and thedegree of activity of the metabolites is unknown Reboxetine has no inhibitory ef-fect on CYP450 isoenzymes Elimination half-life is 13 hr.166

Adverse Reactions The most common adverse effects include dry mouth,

consti-pation, increased sweating, insomnia, and urinary hesitancy, which are greater thanplacebo, but less frequent than imipramine These “anticholinergic-like” effects arebelieved to result from increased norepinephrine levels Side effects commonly as-sociated with serotonin reuptake inhibitors such as nausea, anxiety or agitation, anddaytime somnolence were no more common with reboxetine than with placebo.167

No information is available regarding reboxetine overdose in humans

Pharmacology Sertraline is an SSRI similar to fluoxetine, which indirectly

re-sults in a downregulation of -adrenergic receptors It has no clinically importanteffect on noradrenergic or histamine receptors and no effect on MAO It lacksstimulant, cardiovascular, anticholinergic, and convulsant effects Sertraline hasantidepressant effects equal to TCAs and fluoxetine and might have anorectic ef-fects and efficacy in OCD.130,168–170(See Antidepressants Comparison Chart.)

Administration and Adult Dosage PO for depression, panic disorder, OCD, and posttraumatic stress disorder 50 mg/day initially, increasing if necessary at weekly

intervals to a maximum of 200 mg/day in a single dose in the morning or evening

Dosage Forms Tab 25, 50, 100 mg; Soln 20 mg/mL.

Pharmacokinetics Sertraline has an oral bioavailability of 36%, and, when it is

taken with food, peak serum concentrations and bioavailability increase by 30–40%.Peak serum concentrations are reached in 6–8 hr Sertraline concentrations in breastmilk are the lowest of the SSRIs and produce minimal serum levels in the breast-fedinfant.171Its primary metabolite is N-desmethylsertraline, which has 5–10 times less

activity than sertraline as an SSRI and has no demonstrated antidepressant activity

Cl is decreased by up to 40% in the elderly Steady-state half-life is 27 hr

Adverse Reactions Frequent adverse effects include nausea, diarrhea, ejaculatory

delay, tremor, and increased sweating It causes less agitation, anxiety, and nia than fluoxetine and is a less potent inhibitor of the CYP2D6 isoenzyme at adosage of 50 mg/day Use with caution in patients with renal or hepatic impairmentand do not use it within 14 days of using an MAOI SIADH has been reported.172

insom-Pharmacology Venlafaxine is a potent reuptake inhibitor of serotonin and

nor-epinephrine, like many TCAs, but lacks effects on muscarinic, -adrenergic, orhistamine receptors.173–176(See Antidepressants Comparison Chart.)

Administration and Adult Dosage PO for depression (immediate-release) 75

mg bid or tid initially, increasing q 4–7 days to an effective antidepressant dosage

of 225–375 mg/day in 2 or 3 divided doses; (sustained-release) 75 mg once dailyinitially, increasing in increments of up to 75 mg/day at intervals of 4 or moredays to a maximum of 225 mg/day The sustained-release preparation does not re-

duce side effects but allows once-daily administration PO for generalized

anxi-ety disorder 75–225 mg/day in 2–3 divided doses Patients with renal impairment

or on hemodialysis require a 25–50% dosage reduction

Dosage Forms Tab 25, 37.5, 50, 75, 100 mg; SR Cap 37.5, 75, 150 mg (Effexor

XR)

Pharmacokinetics Venlafaxine is well absorbed orally; food has no effect on

ab-sorption Serum concentrations in elderly patients are no different from those inyounger patients Unlike SSRIs, venlafaxine has minimal protein binding(27–30%) It undergoes extensive hepatic metabolism Venlafaxine has an elimi-nation half-life of 5 hr, and one major active metabolite has an 11-hr half-life.Venlafaxine exhibits linear pharmacokinetics over the recommended dosagerange, and steady state is reached in 3 days

Adverse Reactions Frequent adverse effects include expected serotonin-related

effects (eg, nausea, headache, insomnia or somnolence, and sexual dysfunction)

At higher dosages (375 mg/day), venlafaxine is unique in causing a consistent butmild elevation in diastolic blood pressure (6 mm Hg) Regular blood pressuremonitoring is required for all patients

Drug Interactions Venlafaxine is not a potent inhibitor of the cytochrome P450

enzyme system, making it different from most of the SSRIs Avoid it in patientswho have received an MAOI within the past 14 days

α2-ADRENERGIC BLOCKERS

Remeron rapidly dissolving) 15,

MONOAMINE OXIDASE INHIBITORS (MAOIs)

SELECTIVE SEROTONIN REUPTAKE INHIBITORS (SSRIs)

Celexa Soln 2 mg/mL.

Prozac SR Cap 90 mg

Soln 4 mg/mL Tab 10 mg.

SEROTONIN NOREPINEPHRINE REUPTAKE INHIBITORS (SNRIs)

Imipramine Tab 10, 25, 50 mg 150–300 >200 e Moderate Moderate High

Tofranil Cap (as pamoate)

a Antidepressants with serotonergic activity (SSRIs, nefazodone, venlafaxine, and mirtazapine) have established efficacy for many indications other than depression Some have received

ap-proval from the Food and Drug Administration for generalized anxiety disorder, bulimia nervosa, obsessive-compulsive disorder, social phobia, panic disorder, posttraumatic stress disorder,

and premenstrual dysphoric disorder Effective doses for major depression for most patients are in the low to moderate ranges listed, which is also true for generalized anxiety disorder, social

phobia, panic disorder, and premenstrual dysphoric disorder The middle to high end of the listed dosage ranges is usually necessary for efficacy when treating bulimia nervosa,

obsessive-compulsive disorder, and posttraumatic stress disorder 180

b Not well established.

c Amoxapine, maprotiline, and the tricyclic antidepressants are categorized together as heterocyclic antidepressants because their therapeutic and side effect profiles are similar.

d For obsessive-compulsive disorder.

e Includes active metabolites.

f Major depression.

Antipsychotic Drugs

Class Instructions Antipsychotics This drug can cause drowsiness Until the

extent of this effect is known, use caution when driving, operating machinery, orperforming other tasks requiring mental alertness Avoid excessive concurrent use

of alcohol or other drugs that cause drowsiness

Missed Doses If you miss a dose, take it as soon as you remember If it is almost

time for your next dose, skip it and resume your normal schedule Do not doubledoses

Pharmacology Antipsychotic efficacy is most likely related to blockade of

post-synaptic dopaminergic receptors in the mesolimbic and prefrontal cortexes of thebrain, although other neurotransmitter systems also are involved.181

Administration and Adult Dosage (See Antipsychotic Drugs Comparison Chart

for oral dosage ranges.) Initiate therapy with divided doses until therapeuticdosage is found; then, for most patients, once-daily hs administration is preferred.For maintenance, decrease acute dosage by 25% q 3 months, with a target mainte-nance dosage being 50–67% of the acute treatment dosage.182Recent concern hasfocused on the need to establish a minimum effective dosage for antipsychoticdrugs, and treatment regimens at the low end of the dosage range are preferred

Oral dosages of high-potency antipsychotics (eg, fluphenazine, haloperidol) in

the range of 5–20 mg/day are better tolerated and equal in efficacy to dosages

>20 mg/day.183Most patients can be given a maintenance dosage of 50% the acutedosage by the end of 1 yr, although 10–15% of chronically ill patients require a

maintenance dosage >15 mg/day of haloperidol or its equivalent.184,185For manicepisodes, no additional benefit is achieved with dosages >10 mg/day of haloperi-dol.186Mesoridazine and thioridazine are indicated only in patients who fail with

other drugs because of inefficacy or intolerable side effects

Special Populations Pediatric Dosage As with adults, dosage is determined

pri-marily by titration to individual response No precise dosage range exists, but ingeneral the initial dosage is lower and increased more gradually in children

Geriatric Dosage Initial dosage is 20–25% of the dosage used in younger adults.

Typical starting dosages in the elderly are haloperidol 0.5–2 mg/day Dosage

ad-justments also must be done more slowly than in younger adults.187

Other Conditions Dosages in the lower range are sufficient for most elderly

pa-tients, and the rate of dosage titration is slower

Dosage Forms (See Antipsychotic Drugs Comparison Chart.)

Patient Instructions (See Antipsychotics Class Instructions.) These drugs

usu-ally take several weeks for clinical response and up to 8 weeks for full therapeuticresponse

Pharmacokinetics Onset and Duration Onset of antipsychotic activity is

vari-able, with noticeable response requiring days to weeks

Serum Levels Correlation of serum levels with clinical response is not

consis-tently established The best evidence exists for haloperidol, with serum ANTIPSYCHOTIC DRUGS

concen-trations of 5–15 g/L (13–40 nmol/L) correlating well with therapeutic effects inadult psychotic patients, and an increasing risk of adverse effects and decreasedefficacy when steady-state concentrations exceed 15 g/L.188,189

Fate Haloperidol is well absorbed; peak serum levels are achieved 2–6 hr after

liquid or tablets and within 30 min after IM Oral bioavailability of haloperidol is60–70% Haloperidol is extensively metabolized, with one active hydroxy

metabolite Chlorpromazine and other phenothiazines are well absorbed but

un-dergo extensive and variable presystemic metabolism in the gut wall and liver;more than 20 chlorpromazine metabolites with different activities have been iden-tified in human plasma SR formulations result in a greater first-pass effect

t¹⁄₂ Serum half-lives have no clinical correlation with biologic half-lives for

an-tipsychotic drugs Chlorpromazine serum half-life is 30 hr, thioridazine 4–10

hr, thiothixene 34 hr, and haloperidol 12–24 hr Of more clinical importance is

that steady-state CNS levels and tissue saturation allow once-daily administration

of all antipsychotic drugs.141

Adverse Reactions (See Antipsychotic Drugs Comparison Chart for relative

fre-quency of common adverse reactions.) Frequently, sedation, extrapyramidal fects (eg, parkinsonism, dystonic reactions, akathisia), tardive dyskinesia, anti-cholinergic effects (eg, dry mouth, blurred vision, constipation, urinary retention),photosensitivity, and postural hypotension occur Occasionally, weight gain,amenorrhea, galactorrhea, ejaculatory disturbance, neuroleptic malignant syn-drome, agranulocytosis, skin rash, cholestatic jaundice, and skin or eye pigmenta-tion occur Rarely, seizures, thermoregulatory impairment, and slowed AV con-

ef-duction occur Mesoridazine and thioridazine can prolong QTcinterval, leading

to torsades de pointes and sudden death Low-potency drugs are more likely tocause sedation, anticholinergic effects, and orthostatic hypotension, whereas high-potency drugs cause more extrapyramidal effects Tardive dyskinesia is a long-term adverse effect, untreatable, and sometimes irreversible Tardive dyskinesiaoccurs at a 4% yearly incidence for at least the first 5–6 yr of treatment Neurolep-tic malignant syndrome (ie, fever, extrapyramidal rigidity, autonomic instability,alterations in consciousness) occurs more frequently with high-potency antipsy-chotics, with a prevalence of 1.4% and a fatality rate of 4%.183,190,191

Contraindications Coma; circulatory collapse or severe hypotension; bone

mar-row depression; history of blood dyscrasia (Mesoridazine and thioridazine) current use with drugs that prolong QTcinterval; baseline QTc>450 msec

con-Precautions Use cautiously in patients with myasthenia gravis, Parkinson’s

dis-ease, seizure disorders, or hepatic disease

Drug Interactions Barbiturates can enhance phenothiazine metabolism;

carba-mazepine can enhance haloperidol metabolism Phenothiazines can decrease cacy of guanethidine or guanadrel or have additive hypotensive effects with hy-potensive drugs Phenothiazines can inhibit the antiparkinson activity of levodopa.Haloperidol can increase the CNS toxicity of lithium Combined use of haloperi-dol and methyldopa can result in dementia

effi-Parameters to Monitor (Mesoridazine and thioridazine) obtain baseline and

pe-riodic ECGs and serum potassium

Notes (See also Prochlorperazine Salts in the Antiemetics section for antiemetic

uses.)

Pharmacology Clozapine is an atypical antipsychotic drug that is chemically

similar to loxapine and has unique pharmacologic effects and indications, as well

as very serious adverse effects Whereas typical antipsychotic drugs exert their fects primarily with a blockade of dopamine-D2receptors, clozapine affects sev-eral dopamine and serotonin receptors Its high serotonin-5HT2to dopamine-D2

ef-ratio is the likely explanation for its unique efficacy Compared with traditionalantipsychotic drugs, clozapine is more effective for negative symptoms of schizo-phrenia, is more effective in treatment-resistant patients, and rarely causes ex-trapyramidal effects.192–195

Adult Dosage PO 100–200 mg tid is effective for most patients, but some might

require up to 900 mg/day A therapeutic trial of 12–24 weeks is required for thefull therapeutic effect to become apparent

Dosage Forms Tab 25, 100 mg.

Pharmacokinetics Clozapine is nearly completely absorbed after oral

adminis-tration, with about 30% oral bioavailability because of extensive first-pass olism Clozapine is 95% bound to plasma proteins; with multiple doses, its elimi-nation half-life is 12 hr.196

metab-Adverse Reactions Frequent adverse effects include sedation, orthostatic

hy-potension, anticholinergic effects, fever, and excessive salivation Seizures aredose related, with a frequency up to 5% in the therapeutic dosage range and a 1-yrcumulative incidence of 10% Agranulocytosis is the major adverse effect of con-cern, occurring in 0.8% of patients after 1 yr.197Most cases of agranulocytosisoccur within the first 3 months of therapy Substantial weight gain has been re-ported in most patients receiving clozapine.198(See Antipsychotic Drugs Compari-

son Chart.)

Paramaters to Monitor Patients must have a baseline WBC count and

differen-tial before initiating therapy, mandatory weekly WBC monitoring for the first 6months, and then q 2 weeks throughout treatment and for 4 weeks after discontin-uation

Pharmacology Haloperidol decanoate (HD) is the preferred long-acting depot

antipsychotic drug Depot antipsychotics are indicated only for patients whodemonstrate good response but are consistently drug-noncompliant with resultantfrequent psychotic relapses Depot antipsychotics provide fewer relapses and hos-pitalizations, stable serum drug levels, and side effects equal to oral antipsychotic

drugs HD can be given q 4 weeks; fluphenazine decanoate (FD) is similar in

ef-ficacy and adverse effects, but it must be administered q 2 weeks Do not use HD

or FD to treat acute psychotic symptoms; rather, use the drug only after a patienthas been stabilized on an oral antipsychotic drug.199–203

Adult Dosage IM do not exceed an initial HD dosage of 100 mg, with a target

monthly dosage 20 times the oral haloperidol daily dosage An IM loading dosetechnique has been described that gives 20 times the daily oral dosage, using100–200 mg of depot q 3–7 days to reach the calculated amount, with a maximum

of 450 mg In geriatric or hepatically impaired patients, use a monthly HD dose of

15 times the oral haloperidol dosage Experience with HD doses greater than 500

mg is limited; divide injections >5 mL into 2 equal portions given at 2 sites Oralhaloperidol supplementation might be necessary between monthly injections totreat re-emergence of psychotic symptoms until steady-state concentrations arereached

Dosage Forms Inj 50, 100 mg/mL.

Pharmacokinetics After IM administration of HD, esterases cleave the

de-canoate chain to release the active drug Peak serum concentrations of haloperidoloccur in 3–9 days, with an apparent half-life of 3 weeks; steady-state levels arereached after 12–16 weeks

Adverse Reactions There is no evidence that HD causes adverse effects with a

frequency different from that of oral haloperidol

Pharmacology Olanzapine is an atypical antipsychotic agent that is a potent

serotonin-5HT2and dopamine-D2antagonist It also has anticholinergic and mine H1-receptor antagonistic effects that might account for some of its side ef-fects.204,205(See Antipsychotic Drugs Comparison Chart.)

hista-Adult Dosage PO for psychotic disorders 5–10 mg/day initially (5 mg/day in

patients >65 yr, debilitated patients, or those with a predisposition to hypotensivereactions) Increase in 5 mg/day increments at ≥7-day intervals Usual main-

tenance dosage 10–15 mg/day, to a maximum of 20 mg/day, although dosages

>10 mg/day are generally no more effective than 10 mg/day IM for acute

psy-chosis 2.5–10 mg/dose has been used investigationally.

Dosage Forms Tab (conventional) 2.5, 5, 7.5, 10, 15 mg; (rapidly dissolving)

5, 10, 15, 20 mg (Zyprexa Zydis); Inj (investigational).

Pharmacokinetics Olanzapine is well absorbed orally; food has no effect, but

bioavailability is about 60% because of a first-pass effect It is 93% bound toplasma proteins and has a Vdof about 1000 L The drug is hepatically metabo-lized, probably by CYP1A2 and CYP2D6 Only 7% is excreted unchanged inurine Its half-life is 30 hr

Adverse Reactions Frequent adverse effects include drowsiness, agitation,

ner-vousness, orthostatic hypotension, dizziness, tachycardia, headache, rhinitis, stipation, akathisia, and weight gain As with other atypical antipsychotic drugs,weight gain is the most troublesome long-term adverse effect, often affectingcompliance

con-Drug Interactions Inducers of CYP2D6 may decrease olanzapine serum levels.

Olanzapine does not appear to affect cytochrome P450 enzymes

Pharmacology Pimozide is indicated for the treatment of Tourette’s disorder.

Although structurally different from other antipsychotic drugs, pimozide sharestheir ability to block dopaminergic receptors Its lack of effect on norepinephrinereceptors led to the hope that pimozide would have a more favorable adverse ef-

fect profile than other antipsychotic drugs Haloperidol is the drug of choice for

Tourette’s disorder.206,207

Adult Dosage PO 1–2 mg/day in divided doses initially, with dosage increased

every other day up to a maximum of 20 mg/day Most patients who respond quire ≤10 mg/day Periodically decrease the dosage and attempt to withdraw treat-ment

re-Pediatric Dosage PO 0.05 mg/kg/day initially (preferably hs), increasing q 3

days to a maximum of 0.2 mg/kg or 10 mg daily

Dosage Forms Tab 2 mg.

Pharmacokinetics Pimozide is about 50% absorbed orally It undergoes

exten-sive first-pass metabolism in the liver to two metabolites with unknown activity.The elimination half-life averages 55 hr

Adverse Reactions The relative frequencies of adverse effects of pimozide and

haloperidol are similar, and pimozide remains an alternative to haloperidol fortreating Tourette’s disorder

Pharmacology Risperidone is a potent serotonin-5-HT2 antagonist withdopamine-D2antagonism Whereas typical antipsychotics are dopamine antago-nists, the additional serotonin antagonism increases efficacy for negative symp-toms of schizophrenia and reduces the likelihood of extrapyramidal symptoms.Initial evidence also suggests that risperidone is more effective than traditional an-tipsychotic drugs for treatment-resistant schizophrenic patients.208–211(See An-

tipsychotic Drugs Comparison Chart.)

Adult Dosage PO 1 mg bid initially (0.5 mg bid in the elderly or patients with

se-vere renal or hepatic impairment), increasing q 2–4 days to the usual effectivedosage of 4–6 mg/day in 1 or 2 doses Occasionally, dosages above 6 mg/daymight be necessary, but adverse effects increase and efficacy can be less The so-lution can be mixed with water, coffee, orange juice, or low-fat milk; do not mixwith cola or tea

Dosage Forms Tab 0.25, 0.5, 1, 2, 3, 4 mg; Soln 1 mg/mL.

Pharmacokinetics Risperidone is well absorbed orally The free fraction of

risperidone in serum increases in hepatic disease, necessitating lower dosages It ismetabolized by CYP2D6 to an active metabolite Risperidone’s elimination half-life is 3 hr; its active metabolite has a half-life of 24 hr The half-lives of one orboth are prolonged in patients with renal disease.212

Adverse Reactions Frequent dose-related adverse effects are extrapyramidal

ef-fects, orthostatic hypotension, headache, rhinitis, and insomnia

Drug Interactions Inhibitors of CYP2D6 can increase risperidone levels and

have adverse effects

Pharmacology Ziprasidone is an atypical antipsychotic drug with a very high

ratio of 5-HT2Ato dopamine-2 blockade, suggesting a very low risk of pyramidal effects In addition, it is a 5-HT1Aagonist like buspirone, and inhibitsreuptake of both serotonin and norepinephrine like antidepressants The clinicalvalue of the latter two effects are not established.213

extra-Adult Dosage PO as an antipsychotic 20 mg bid with food initially, increasing

as necessary at intervals of at least 2 days to a maximum of 80 mg bid

Mainte-nance dosage may be as low as 40 mg/day IM ziprasidone for acute agitation

in a psychotic patient 10–20 mg, may repeat in 2–4 hr.213

Dosage Forms Cap 20, 40, 60, 80 mg; Inj investigational.

Patient Instructions (See Antipsychotics Class Instructions.) Take this

medica-tion with food

Pharmacokinetics Oral bioavailability is 60% when taken with food With oral

twice daily administration, peak blood levels occur at 6–8 hr Ziprasidone is tabolized by aldehyde oxidase and to a lesser extent by CYP3A4 to inactivemetabolites The elimination half-life is 5–10 hr (range 3–18) for oral ziprasidoneand 3 hr for IM ziprasidone The pharmacokinetics are unaffected by sex, age, ormoderate renal or hepatic disease

me-Adverse Reactions Extrapyramidal effects are minimal, but comparative data

with other atypical antipsychotic drugs are not available A major potential tage of ziprasidone is that it is the least likely atypical antipsychotic drug to causeweight gain.214Compared to placebo, the only side effect greater with ziprasidone

advan-is sedation Ziprasidone increases the QTcinterval by up to 14 msec Ziprasidoneshould be avoided in patients with pre-existing QTcprolongation, after acute MI,

in severe CHF, and in patients taking other drugs that prolong the QTcinterval

>500 msec

DRUG DOSAGE RANGE ANTIPSYCHOTIC USUAL SINGLE Orthostatic

AND CLASS FORMS (MG/DAY) DOSE (MG) IM DOSE (MG) Sedation Anticholinergic Extrapyramidal Hypotension

SR Cap not recommended.

DOSAGE EQUIVALENT

AND CLASS FORMS (MG/DAY) DOSE (MG) IM DOSE (MG) Sedation Anticholinergic Extrapyramidal Hypotension

DRUG DOSAGE RANGE ANTIPSYCHOTIC USUAL SINGLE Orthostatic

AND CLASS FORMS (MG/DAY) DOSE (MG) IM DOSE (MG) Sedation Anticholinergic Extrapyramidal Hypotension

DOSAGE EQUIVALENT

AND CLASS FORMS (MG/DAY) DOSE (MG) IM DOSE (MG) Sedation Anticholinergic Extrapyramidal Hypotension

a At dosages over 6 mg/day, nausea and insomnia are limiting side effects; extrapyramidal symptoms markedly increase at dosages over 6 mg/day.

From references 181–183, 192, 196, 200, 201, 209, and 215–219.

Anxiolytics, Sedatives, and Hypnotics

Class Instructions Sedatives and Hypnotics This drug causes drowsiness and

can produce sleep Do not exceed the prescribed dosage and use caution whendriving, operating machinery, or performing other tasks requiring mental alertness.Avoid concurrent use of alcohol or other drugs that cause drowsiness or sleep Donot abruptly stop taking this medication; the dosage must be decreased slowly

Missed Doses If you miss a dose, take it as soon as you remember If it is almost

time for your next dose, skip it and resume your normal schedule Do not doubledoses

Pharmacology Alprazolam is a triazolobenzodiazepine that is equal in efficacy

to other benzodiazepines for generalized anxiety disorder but more effective in thetreatment of panic disorder Although alprazolam has some efficacy in major de-pression, it is less effective than heterocyclic antidepressants.220,221(See also

Clonazepam, and the Benzodiazepines and Related Drugs Comparison Chart.)

Adult Dosage PO for generalized anxiety disorder 0.25 mg tid initially,

in-creasing gradually to 4 mg/day PO for panic disorder 0.5 mg tid is

recom-mended initially; most panic patients require 5–6 mg/day, and occasionally

10 mg/day can be needed for full response SL alprazolam tablets can be

adminis-tered SL with no difference from oral administration in onset, peak, or cokinetics.222 Discontinuation decrease the daily dosage by no more than

pharma-0.5 mg/day q 3 days until the daily dosage reaches 2 mg and then decrease dosage

in 0.25 mg/day increments q 3 days

Dosage Forms Tab 0.25, 0.5, 1, 2 mg; Soln 0.1, 1 mg/mL.

Pharmacokinetics Like diazepam, alprazolam has a rapid onset of effect after

oral administration, but its shorter life requires tid administration The life is 11 hr in adults; the elderly might have decreased clearance and an increasedhalf-life of 21 hr.221–223

half-Adverse Reactions (See Benzodiazepines.) Patients do not show complete

cross-tolerance between triazolobenzodiazepines and other benzodiazepines, but

clo-nazepam has been shown to be an effective long–half-life substitute drug for use

in alprazolam withdrawal.224

Pharmacology Benzodiazepines have a more specific anxiolytic effect than

other sedatives Benzodiazepines facilitate the inhibitory effect of GABA on ronal excitability by increasing membrane permeability to chloride ions.225

neu-Administration and Adult Dosage (See Benzodiazepines and Related Drugs

Comparison Chart.) Optimal oral use requires individual dosage titration to cal response The long-acting drugs can be administered once daily hs; the short-

clini-acting drugs require multiple daily doses (See Benzodiazepines and Related

Drugs Comparison Chart.) Determine the dosage schedule by the individual

pa-BENZODIAZEPINES

tient’s relative degree of dysfunction from daytime anxiety compared with nia Despite physiologic dependence, benzodiazepines might need to be used formonths and sometimes years for treatment of panic disorder and generalized anxi-ety disorder; situational anxiety, adjustment disorders, and anxiety secondary toother causes require only days to weeks of drug treatment.226PO for alcohol withdrawal evidence suggests no superiority of any benzodiazepine in alcohol

insom-withdrawal, although chlordiazepoxide has been most adequately studied;

(chlordiazepoxide) 25–100 mg for agitation, anxiety, and tremor; on the first day,

up to 400 mg can be given in divided doses, with gradual dosage reductions over

4 days; (diazepam) 5–20 mg for agitation, anxiety, and tremor; alternatively, it

can be given in 20 mg doses q 2 hr until complete suppression of signs and toms is achieved After this loading dose, further administration is unnecessary;227

symp-(oxazepam) 15–60 mg q 4–6 hr for agitation, anxiety, and tremor Oxazepam is

preferred in patients with severe liver disease IM chlordiazepoxide is not mended because of slow, erratic absorption; however, lorazepam is suitable for

recom-IM administration.141,227Diazepam injectable solution (Valium, various) can be

administered IM or IV; the injectable emulsion (Dizac) is for IV use only (do not

administer IM or SC); neither the solution nor the emulsion should be tered faster than 5 mg/min into a peripheral vein, and small veins should beavoided; neither product is recommended to be added to other drugs or solutions

adminis-(See Fate.) PR diazepam for seizures 0.2 mg/kg of Diastat rectal gel, rounded

up to the next dosage size (2.5, 5, 10, 15, 20 mg); an additional dose can begiven 4–12 hr after the first dose Treat no more than 1 episode q 5 days or

5 episodes/month with Diastat

Special Populations Pediatric Dosage PO (diazepam, >6 months) 1–2.5 mg tid

or qid Most benzodiazepines are not recommended in children because of cient clinical experience and concern about the stimulating and paradoxical effects

insuffi-that occur because of disinhibition Midazolam is commonly used in children for

preanesthetic sedation (See Midazolam.) PR diazepam for seizures (2–5 yr)

0.5 mg/kg of Diastat rectal gel, rounded up to the next dosage size (2.5, 5, 10, 15,

20 mg); (6–11 yr) 0.3 mg/kg of Diastat rectal gel, rounded up to the next dosagesize An additional dose may be given 4–12 hr after the first dose Treat no morethan 1 episode q 5 days or 5 episodes/month with Diastat

Geriatric Dosage The elderly might have reduced clearance and enhanced CNS

sensitivity, which requires initial dosage to be reduced by 33–50%.228

Other Conditions Higher dosages might be needed in heavy smokers Patients

with liver disease might have reduced clearance and/or enhanced CNS sensitivity,which requires reduction of initial and subsequent doses Alcoholic patients withreduced plasma proteins might require a lower dosage because of decreased pro-tein binding

Dosage Forms (See Benzodiazepines and Related Drugs Comparison Chart.) Patient Instructions (See Sedatives and Hypnotics Class Instructions.) Pharmacokinetics Serum Levels Not used clinically.

Fate Diazepam and chlordiazepoxide are absorbed faster and more completely

orally than intramuscularly Lorazepam and midazolam have rapid and reliable

IM absorption.141,229(See Benzodiazepines and Related Drugs Comparison Chart.)

Adverse Reactions Frequent effects include drowsiness, dizziness, ataxia, and

disorientation; these effects rarely require drug discontinuation and are easilymanaged by dosage reduction Anterograde amnesia is frequent.141Occasionally,agitation and excitement occur.230With parenteral therapy, hypotension and respi-ratory depression occur occasionally Rarely, hepatotoxicity or blood dyscrasiasoccur Diazepam emulsion is associated with less venous thrombosis and phlebitisthan the solution, which can be very irritating to veins

Contraindications Acute narrow-angle glaucoma; (diazepam emulsion injection)

hypersensitivity to soy protein

Precautions Pregnancy; impaired hepatic function Abrupt drug withdrawal can

result in rebound insomnia, abstinence syndrome similar to barbiturate drawal, seizures, or, rarely, psychosis Patients do not show complete cross-tolerance between triazolobenzodiazepines and other benzodiazepines History ofsubstance abuse can indicate increased likelihood of benzodiazepine misuse.225

with-Drug Interactions Concurrent use with other CNS depressants can potentiate the

sedation caused by benzodiazepines Nefazodone inhibits alprazolam and lam metabolism; fluoxetine and fluvoxamine increase levels of alprazolam and di-azepam; omeprazole increases serum diazepam levels

triazo-Parameters to Monitor Periodically reassess the need for therapy during

long-term use

Pharmacology Buspirone is the first of a class of selective serotonin-5-HT1Aceptor partial agonists It also has some effect on dopamine-D2autoreceptors and,like antidepressants, can downregulate -adrenergic receptors Unlike benzodi-azepines, it lacks amnestic, anticonvulsant, muscle relaxant, and hypnotic effects.Its exact anxiolytic mechanism of action is complex and not clearly defined.231,232

re-Administration and Adult Dosage PO for anxiety 5 mg tid or 7.5 mg bid for

1 week, increasing in 5 mg/day increments q 2–3 days to a maximum of 60 mg/day

in 2 or 3 divided doses Most patients require 20–30 mg/day in divided doses

Special Populations Pediatric Dosage Safety and efficacy not established.

Geriatric Dosage Same as adult dosage.

Other Conditions Decrease the initial dose to 5 mg bid in patients with hepatic or

renal impairment.231,233

Dosage Forms Tab 5, 7.5, 10, 15 mg.

Patient Instructions This drug requires several weeks of continuous use for

ther-apeutic effect and is not effective when used intermittently

Pharmacokinetics Onset and Duration Onset of anxiolytic effect can take

sev-eral weeks

Fate The drug is well absorbed; oral bioavailability is 3.9 ± 4.3% Administration

after meals increases bioavailability by 80% It is extensively metabolized by dative dealkylation pathways.234

oxi-t¹⁄₂ 2.1 ± 1.2 hr.234

Adverse Reactions Dosages >60 mg/day can cause dysphoria.225Frequent sea, dizziness, headache, and insomnia occur Unlike benzodiazepines, buspironedoes not cause dependence or withdrawal effects.231,235

nau-Contraindications None known.

Precautions Buspirone has no cross-tolerance with benzodiazepines, so patients

being switched from a benzodiazepine should have their dosages of the azepine decreased slowly

benzodi-Drug Interactions Unlike benzodiazepines, buspirone does not interact with

al-cohol.231,235Buspirone can increase haloperidol serum levels Avoid concurrentbuspirone and an MAOI because the combination can cause hypertension

Parameters to Monitor Monitor renal and hepatic function initially and

periodi-cally during long-term therapy

Notes Buspirone is indicated only for the treatment of generalized anxiety

disor-der and is not effective as a prn medication or hypnotic Buspirone’s anxiolytic fect without sedation or respiratory depression has led to its use in agitation andanxiety, dementia, mental retardation, and spinal cord injury Its unique effect onthe 5-HT1Areceptor has led to uncontrolled studies and clinical use for premen-strual tension syndrome and to decrease craving in smoking cessation.236

ef-Pharmacology Flumazenil is a selective inhibitor of the CNS effects of

benzodi-azepine sedatives It competitively blocks the effect of benzodibenzodi-azepines and dem on GABA-mediated inhibitory pathways within the CNS Flumazenil findsits greatest use in the reversal of benzodiazepine sedation after medical and surgi-cal procedures and occasionally in the management of benzodiazepine over-dose.237-239

zolpi-Adult Dosage IV for reversal of conscious sedation 0.2 mg over 15 sec; this

dose can be repeated after 45 sec and every minute thereafter prn, to a total dosage

of 1 mg IV for benzodiazepine overdose 0.2 mg over 30 sec, followed, if

neces-sary, by 0.3 mg after 30 sec Further doses of 0.5 mg over 30 sec can be given at1-min intervals to a cumulative dosage of 3 mg Rarely, patients who respond par-tially to 3 mg respond more completely to a dosage of 5 mg If resedation occursafter either use, additional doses of up to 1 mg can be given at 20-min intervals to

a maximum of 3 mg/hr Flumazenil does not consistently reverse benzodiazepineamnesia, so give patients written instructions to avoid operation of motor vehicles

or hazardous equipment, or ingestion of alcohol or nonprescription medicationsfor 18–24 hr, or longer if benzodiazepine effects persist

Dosage Forms Inj 0.1 mg/mL.

Pharmacokinetics Reversal of benzodiazepine coma can occur within 1–2 min

and last 1–5 hr, depending on the dosages of the benzodiazepine and flumazenil

First-pass hepatic metabolism limits the bioavailability of oral flumazenil, so thedrug is administered by IV injection It is rapidly hydroxylated in the liver to inac-tive metabolites Vdis 0.6–1.6 L/kg; its elimination half-life is 0.7–1.3 hr.

Adverse Reactions Frequent side effects have been minimal and are usually

lim-ited to nausea and vomiting, anxiety, and agitation However, seizures have curred, most often in patients on long-term benzodiazepine therapy or after over-dose with heterocyclic antidepressants or other potentially convulsant drugs (eg,bupropion, cocaine, cyclosporine, isoniazid, lithium, methylxanthines, MAOIs,propoxyphene) Be prepared to manage seizures before giving flumazenil.240

oc-Pharmacology Midazolam is a short-acting triazolobenzodiazepine for use in

anesthesia It is unique in its physicochemical properties; at a pH under 4 the drugexists as a highly water-soluble, stable compound, but at physiologic pH, it be-comes lipophilic This allows IV administration of a water-soluble, rapidly actingdrug with a very low frequency of venous irritation Midazolam is given IM forpreoperative sedation and IV for induction of anesthesia or for conscious sedationfor endoscopy and other procedures.241-243

Adult Dosage IM for preoperative sedation 0.07–0.08 mg/kg (about 5 mg) 1 hr

before surgery IV for endoscopy and other conscious sedation procedures

dosage must be individualized and not administered by rapid bolus Titrate slowly

to desired effect; some patients might respond to as little as 1 mg Give no morethan 2.5 mg over at least 2 min as the 1 mg/mL (or more dilute) solution; in el-derly, debilitated, or chronically ill patients, limit the initial dose to 1.5 mg Fur-ther small doses can be given after waiting at least 2 min Do not give the drug IVwithout oxygen and resuscitation equipment immediately available

Pediatric Dosage PO for sedation (6 mo–16 yr) 0.25–1 mg/kg (usually

0.5 mg/kg) to a maximum of 20 mg PR for preanesthetic sedation 0.3 mg/kg as

a solution diluted in 5 mL of saline is a safe and effective alternative to IM istration.244

admin-Dosage Forms Inj 1, 5 mg/mL; Syrup 2 mg/mL.

Pharmacokinetics Midazolam is >90% absorbed after IM injection; peak serum

levels occur within 30 min Peak levels after IM administration are about 50% of

IV levels PO onset is 10–20 min; IM onset is about 15 min The drug is 97%bound to plasma proteins and has a Vdof 1–3 L/kg; Cl is 0.25–0.54 L/hr/kg.Midazolam is hepatically metabolized via CYP3A4 to the 1-hydroxy- and 4-hydroxy-metabolites; the 1-hydroxy-metabolite is at least as active as midazo-lam Midazolam’s half-life is 1.8–6.4 hr

Adverse Reactions Respiratory depression and respiratory arrest occur

fre-quently Impairment of psychomotor skills continues after acute sedation haspassed, so patients should not drive or operate machinery until it is clear that theyhave recovered fully

Pharmacology Triazolam is a triazolobenzodiazepine hypnotic whose effect is

likely related to its facilitation of GABA-mediated neurotransmission, but itsexact mechanism is unknown

Administration and Adult Dosage (See Benzodiazepines and Related Drugs

Comparison Chart.) PO as a hypnotic 0.25 mg hs initially; do not exceed 0.5 mg.

Special Populations Pediatric Dosage (<18 yr) safety and efficacy not established Geriatric Dosage PO decrease initial dose to 0.125 mg, increase if necessary to

0.25 mg hs.245,246

Other Conditions PO 0.125 mg initially in debilitated patients and those with low

body weights or with hepatic impairment

Dosage Forms Tab 0.125, 0.25 mg.

Patient Instructions (See Sedatives and Hypnotics Class Instructions.) Pharmacokinetics Onset and Duration Onset of hypnotic effect is 0.5–1 hr, with

peak serum levels achieved within 2 hr

Fate Oral bioavailability 44%, SL 53%, because of nonhepatic presystemic

me-tabolism Vdis 1.2 ± 0.5 L/kg; Cl is 0.34 ± 0.2 L/hr/kg Cl decreases with ing age (attributed to reduced hepatic oxidizing capacity in the elderly) Triazolamundergoes hydroxylation and rapid conjugation Smoking does not affect elimina-tion.118,247Accumulation does not occur with multiple doses

advanc-t¹⁄₂ 2.6 ± 1 hr Half-life is not affected by end-stage renal disease or liver

dis-ease.118,247,248

Adverse Reactions Frequently, anterograde amnesia,249 daytime anxiety, andataxia occur Occasionally, agitation, confusion, or mood disturbance occur.Rarely, respiratory depression, depersonalization, and derealization, or psychosisoccur Unlike other benzodiazepines, several fatalities have been reported in el-derly patients who overdosed on triazolam.250,251

Contraindications Pregnancy.

Precautions Pregnancy; impaired hepatic function Abrupt drug withdrawal can

result in rebound insomnia, abstinence syndrome similar to barbiturate withdrawal,seizures, or, rarely, psychosis Patients do not show complete cross-tolerance be-tween triazolam and other benzodiazepines History of substance abuse can indicate

an increased likelihood of triazolam misuse.225Do not prescribe the drug for morethan 7–10 days of consecutive therapy or in quantities larger than a 30-day supply

Drug Interactions Concurrent use with other CNS depressants can potentiate the

sedation caused by benzodiazepines Nefazodone inhibits triazolam metabolism

Notes Compared with other benzodiazepine hypnotics, triazolam is equally

ef-fective in reducing sleep latency and less likely to cause daytime sedation; ever, it is less likely to prevent early morning awakening and more likely to causerebound insomnia Hypnotic drugs are most effective when used to treat transientsituational insomnia (1–3 days) and short-term insomnia (1–3 weeks maxi-mum).251,252

Pharmacology Zaleplon is a nonbenzodiazepine hypnotic that, like zolpidem,

se-lectively binds only to the 1receptor This selectivity suggests a sedative effectwith less potential for memory impairment, interaction with alcohol, and psy-chomotor effects than with benzodiazepines.253

Administration and Adult Dosage PO as a hypnotic 10 mg hs initially (5 mg in

the elderly) Because of its very rapid onset and offset, zaleplon can be given ing the night after the patient experiences difficulty falling asleep rather thanbeing given before bedtime in anticipation of sleep difficulty Zaleplon can begiven during the night without morning hangover as long as there are 4 hr remain-ing in bed after administration

dur-Dosage Forms Cap 5, 10 mg.

Pharmacokinetics After oral administration, zaleplon reaches peak serum

con-centrations in 1.1 hr Zaleplon is metabolized by CYP3A4 but has no activemetabolites Its half-life is 0.8–1.4 hr (average 1).254

Adverse Reactions Dose-related side effects include dizziness, headache, and

somnolence Symptoms begin to appear approximately 30 min after a dose, peak

at 1–2 hr, and are no longer evident at 4 hr After a 10-mg dose, zaleplon has noresidual effects on performance and memory tests after 2 hr; in contrast, residualeffects persist for up to 5 hr with zolpidem.255

Pharmacology Zolpidem is a short-acting nonbenzodiazepine hypnotic indicated

for the short-term treatment of insomnia Most benzodiazepines bind to allGABA-benzodiazepine () receptor complexes, but zolpidem selectively bindsonly to the 1receptor This difference suggests a more selective sedative–hypnotic effect without anxiolytic, anticonvulsant, or muscle relaxant ef-fects.256–258(See Benzodiazepines and Related Drugs Comparison Chart.)

Adult Dosage PO as a hypnotic 10 mg immediately before bedtime In the

el-derly, patients with hepatic impairment, or patients taking other CNS depressants,the dose is 5 mg

Dosage Forms Tab 5, 10 mg.

Pharmacokinetics After oral administration, zolpidem reaches peak serum

con-centrations in 1.6 hr, is 93% bound to plasma proteins, has no active metabolites,and has an elimination half-life of 1.5–4 hr (average 2.5) Half-life is increased byone-third in the elderly and greatly increased in patients with hepatic impairment(9.9 hr)

Adverse Reactions Dose-related side effects include daytime drowsiness,

dizzi-ness, and diarrhea Clinical trials with 20 mg doses have reported headache, sea, memory problems, and CNS stimulation Tolerance has not been reported,nor has rebound insomnia after therapeutic doses Psychomotor performance isimpaired when zolpidem is combined with alcohol Efficacy has been demon-strated for 35 nights at doses of 10 mg without affecting sleep stages or psy-chomotor performance

BENZODIAZEPINES AND RELATED DRUGS COMPARISON CHART

BENZODIAZEPINES AND RELATED DRUGS COMPARISON CHART (continued )

a Controlled substance schedule designated after each drug (in parentheses).

b Parent drug plus active metabolites.

c For generalized anxiety disorder.

d For panic disorder.

e Also used as an IV anesthetic; well absorbed IM.

f Hydrolyzed to nordazepam (desmethyldiazepam) before absorption.

g Not a benzodiazepine chemically, but an imidazopyridine, which is a selective benzodiazepine-1 receptor agonist.

h Rapidly and completely metabolized to desalkylflurazepam.

From references 221, 222, 225, 229, 241, 247, 249, and 258–262.

SEDATIVES AND HYPNOTICS COMPARISON CHART

ADULT

Tab 8, 15, 16, 30, 60,

90, 100 mg Inj 30, 60, 65,

130 mg/mL.

HYPNOTICS

Syrup 50, 100 mg/mL.

Seconal

Various

a Controlled substance schedule designated after each drug (in parentheses).

From references 251, 252, 262, and 263.

Pharmacology Lithium’s mechanism of antimanic effect is unknown; it alters

the actions of several second-messenger systems (eg, adenylate cyclase and phoinositol).264,265

phos-Administration and Adult Dosage Individualize dosage according to serum

lev-els and clinical response Acute manic episodes typically require PO 1.2– 2.4 g/day; maintenance therapy requires 900 mg–1.5 g/day A loading dose of

30 mg/kg, in 3 divided doses, can be given to achieve the desired serum levelwithin 12 hr.266A number of predictive dosage techniques have been developedbased on estimated steady state after one serum level.267,268

Special Populations Pediatric Dosage PO (<12 yr) 15–20 mg (0.4–

0.5 mEq)/kg/day in 2–3 divided doses; (12–18 yr) same as adult dosage.269

Geriatric Dosage (>65 yr) decrease adult dosage by 33–50%.270

Other Conditions Adjust the dosage more carefully in patients with decreased

renal function and in patients receiving thiazide diuretics or NSAIDs

Dosage Forms Cap 150, 300, 600 mg; Tab 300 mg; SR Tab 300, 450 mg; Syrup 1.6 mEq/mL (as citrate).

Patient Instructions This drug can be taken with food, milk, or antacid to

mini-mize stomach upset Report immediately if signs of toxicity occur, such as tent diarrhea, vomiting, coarse hand tremor, drowsiness, or slurred speech, or be-fore beginning any diet In hot weather, ensure adequate water and salt intake

persis-Pharmacokinetics Onset and Duration Onset 7–10 days for therapeutic effect.141

Serum Levels (Acute mania or hypomania) 0.8–1.5 mEq/L; (prophylaxis) 0.6–

1.2 mEq/L, although concern about long-term renal effects suggests most patientsshould be maintained <0.9 mEq/L Levels >1.5 mEq/L are regularly associatedwith some signs of toxicity, and levels >2 mEq/L result in serious toxicity.271(See

Adverse Reactions.)

Fate Absorption is virtually complete within 8 hr after oral administration, with

peak levels occurring in 2–4 hr Distribution is throughout total body water, buttissue uptake is not uniform The drug is not protein bound or metabolized, butfreely filtered through the glomerulus, with about 80% being reabsorbed

t¹⁄₂ 18–20 hr; up to 36 hr in the elderly.141

Adverse Reactions Frequent, dose-related effects with therapeutic serum levels

include nausea, diarrhea, polyuria, polydipsia, fine hand tremor, and muscle ness Signs of toxicity include coarse hand tremor, persistent GI effects, muscle hy-perirritability, slurred speech, confusion, stupor, seizures, increased deep tendonreflexes, irregular pulse, and coma Frequent, non–dose-related effects include nontoxic goiter, hypothyroidism, nephrogenic diabetes insipidus-like syndrome,

folliculitis, aggravation of acne or psoriasis, leukocytosis, hypercalcemia, andweight gain.272,273

Contraindications Pregnancy; fluctuating renal function; severe renal or

cardio-vascular disease

Precautions Use with caution in patients with cardiac disease, dehydration,

sodium depletion, diuretic therapy, or dementia, in nursing mothers, and in the

el-derly (See Special Populations.)

Drug Interactions ACE inhibitors can increase serum lithium concentrations.

Theophylline or excess sodium enhance renal lithium clearance; sodium ciency can promote lithium retention and increase risk of toxicity Long-term di-uretic or NSAID use can result in decreased lithium elimination Haloperidol canincrease the CNS toxicity of lithium; with methyldopa or phenytoin, signs oflithium toxicity can occur without increased serum lithium

defi-Parameters to Monitor Prelithium workup should include thyroid function tests,

Crs, BUN, CBC (for baseline WBC count), urinalysis (for baseline specific ity), electrolytes, and ECG (if patient is older than 40 yr) During therapy, obtainserum lithium levels (drawn 12 hr after last dose) weekly during initiation andmonthly during maintenance.274,275

grav-Notes Divalproex sodium is equivalent in efficacy to lithium for bipolar

disor-der and more effective than lithium for rapid-cycling bipolar illness.276–278

Neurodegenerative Disease Drugs

Pharmacology Amantadine is an antiviral compound that prevents the release of

viral nucleic acid into the host cell In Parkinson’s disease, the drug increasespresynaptic dopamine release, blocks the reuptake of dopamine into the presyn-aptic neurons, and exerts anticholinergic effects Amantadine also can reducelevodopa-induced dyskinesias in patients with Parkinson’s disease, possibly byacting as an N-methyl-D-aspartate receptor antagonist.279,280

Administration and Adult Dosage PO for Parkinson’s disease, give 100

mg/day initially, increasing in 100 mg/day increments q 7–14 days to effective

dosage, or to a maximum of 300 mg/day in divided doses Usual maintenance

dosage 100 mg bid PO for extrapyramidal reactions 100 mg bid, to a

maxi-mum of 300 mg/day in 3 divided doses PO for prophylaxis of influenza A

200 mg/day in 1–2 divided doses continuing for at least 10 days after exposure,for 2–3 weeks after giving influenza A vaccine, or for up to 90 days when vaccine

is unavailable or contraindicated PO for treatment of influenza A 200 mg/day

in 1–2 divided doses starting within 24–48 hr after onset of illness and continuingfor 24–48 hr after symptoms disappear

Special Populations Pediatric Dosage PO for prophylaxis or treatment of

in-fluenza A (<1 yr) safety and efficacy not established; (1–9 yr) 4.4–8.8 mg/kg/day

in 2 divided doses, to a maximum of 150 mg/day; (9–12 yr) 100 mg bid For phylaxis, continue therapy for at least 10 days after exposure, for 2–3 days after

giving influenza A vaccine, or for up to 90 days when vaccine is unavailable orcontraindicated For treatment, continue for 24–48 hr after symptoms disappear.

Geriatric Dosage PO for influenza prophylaxis or treatment (>65 yr)

100 mg/day PO for Parkinson’s disease same as adult dosage, adjusting for

renal impairment

Other Conditions Reduce dosage in renal impairment as follows: with Clcrof30–50 mL/min, give 200 mg first day and then 100 mg/day; with Clcrof 15–

29 mL/min, give 200 mg first day and then 100 mg every other day; with Clcr

<15 mL/min or for patients on hemodialysis, give 200 mg q 7 days

Dosage Forms Cap 100 mg; Syrup 10 mg/mL.

Patient Instructions This medication can cause dizziness, confusion, or

diffi-culty in concentrating Until the extent of these effects is known, use caution whendriving, operating machinery, or performing other tasks requiring mental alert-

ness Avoid excessive concurrent use of alcohol Parkinson’s disease Stopping

this medication suddenly can cause your Parkinson’s disease to worsen

Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is about time for the next dose, take that dose only Donot double the dose or take extra

Pharmacokinetics Onset and Duration Antiparkinson effects disappear in most

patients after 6–12 weeks of therapy.281

Serum Levels (Therapeutic trough, antiviral) 300 g/L (2 mol/L)

Fate Peak serum levels occur in 1–4 hr in young adults, 4.5–7 hr in older adults.

Steady-state serum levels occur in healthy volunteers and Parkinson’s patientswithin 4–7 days;282Vdis 6.6 ± 1.5 L/kg; Cl is 0.39 ± 0.13 L/hr/kg with normalrenal function From 78% to 88% is excreted unchanged in urine.283

t¹⁄₂ (Healthy young adults) 11.8 ± 2.1 hr,284(elderly adults) 31 ± 7.2 hr,285(duringchronic hemodialysis) 8.3 ± 1.5 days.284

Adverse Reactions Nausea, dizziness, insomnia, confusion, hallucinations,

anxi-ety, restlessness, depression, irritability, peripheral edema, orthostatic sion, or livedo reticularis occur frequently Occasionally, CHF, psychosis, urinaryretention, or reversible elevation of liver enzymes can occur Seizures, cornealopacities, or leukopenia rarely occur

hypoten-Drug Interactions Amantadine can potentiate the CNS effects of anticholinergic

agents

Precautions Pregnancy; lactation Use with caution in patients with CHF,

seizures, renal or hepatic disease, peripheral edema, orthostatic hypotension, chosis, or history of eczematoid rash or in those receiving CNS stimulants Abruptdrug discontinuation in patients with Parkinson’s disease can result in rapid clini-cal deterioration Observe patients carefully when dosages of amantadine are re-duced abruptly or discontinued, especially if patients are receiving neuroleptics.Sporadic cases of neuroleptic malignant syndrome have been reported in associa-tion with amantadine withdrawal or dosage reduction Suicide attempts have beenreported in patients treated with amantadine, including short influenza treatment,

psy-and in patients with psy-and without psychiatric histories Amantadine can exacerbatemental problems in patients with psychiatric disorders.

Parameters to Monitor Monitor renal function and disease symptoms

periodi-cally in parkinsonian patients

Notes In Parkinson’s disease, amantadine is indicated as initial treatment alone or in

combination with levodopa Amantadine produces clinical improvements in akinesia

and rigidity, but to a lesser degree than levodopa.281,282Amantadine also can be ficial in Parkinson’s disease patients with nighttime monoclonus, freezing, or dysto-nia There is no evidence that amantadine alters the course of Parkinson’s disease

bene-Anticholinergics appear to reduce tremor to a greater degree than amantadine Rimantadine (Flumadine) is an antiviral compound with efficacy similar to

amantadine against influenza A It appears to be slightly better tolerated thanamantadine Dosage is 100 mg bid in adults In elderly nursing home patients orthose with severe hepatic dysfunction or renal failure (Clcr≤10 mL/min), reducedosage to 100 mg/day In children younger than 10 yr (prophylaxis only), give

5 mg/kg once daily, not to exceed 150 mg For children 10 yr and older, use theadult dose Available as 100 mg tablets and 10 mg/mL syrup

Pharmacology Benztropine is a synthetic competitive antagonist of

acetyl-choline In Parkinson’s disease, the drug reduces the relative excess of cholinergicactivity in the basal ganglia that develops because of absolute dopamine defi-ciency in this area

Administration and Adult Dosage PO, IM, or IV for Parkinson’s disease

0.5–1 mg/day initially, increasing in 0.5 mg/day increments q 5–6 days to

effec-tive dosage, to a maximum of 6 mg/day Usual maintenance dosage 1–2 mg/day

in 2–3 divided doses When used concurrently with levodopa, the dosages of both

drugs might require reduction PO, IM, or IV for drug-induced extrapyramidal

disorders 1–4 mg/day in 1–2 doses.

Special Populations Pediatric Dosage (<3 yr) contraindicated; (>3 yr) 0.02–

0.05 mg/kg/dose once or twice daily

Geriatric Dosage Same as adult dosage, although older patients often can be

con-trolled with 1–2 mg/day Some consider it best to avoid this drug in the elderly.286

Dosage Forms Tab 0.5, 1, 2 mg; Inj 1 mg/mL.

Patient Instructions This drug can cause constipation, difficult or painful

urina-tion, dry mouth, blurred vision, or drowsiness Use caution when driving, ing machinery, or performing other tasks requiring mental alertness Avoid exces-sive concurrent use of alcohol and other drugs that cause drowsiness

operat-Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is about time for the next dose, take that dose only Donot double the dose or take extra

Pharmacokinetics Onset and Duration Onset of resolution of drug-induced

ex-trapyramidal symptoms is within 15 min after IV or IM administration and 1–2 hrafter oral administration Duration is 24 hr.269

Fate Benztropine pharmacokinetics are not well studied, but the drug apparently

is hepatically metabolized to conjugates and might undergo enterohepatic cling.287

recy-Adverse Reactions Frequent adverse effects are dose related and include dry

mouth, blurred vision, nausea, dizziness, constipation, nervousness, and urinaryretention Confusional states, impairment of recent memory, and hallucinationsoccur with use of high doses and in patients with advanced age and underlying de-mentia Rarely, paralytic ileus, parotitis, hyperthermia, or skin rash occurs

Contraindications Children <3 yr; narrow-angle glaucoma; pyloric or duodenal

obstruction; stenosing peptic ulcers; achalasia; bladder-neck obstructions; thenia gravis; cognitive disturbances.286

myas-Precautions Pregnancy; elderly patients Use with caution in hot weather or

dur-ing exercise and in patients with tachycardia, prostatic hypertrophy, open-angleglaucoma, or obstructive diseases of the GI tract

Drug Interactions Carefully observe patients given concomitant phenothiazines

and/or heterocyclic antidepressants because intensification of mental symptoms,paralytic ileus, or hyperthermia can occur Anticholinergics can decrease the ef-fectiveness of phenothiazines Use with amantadine can result in increased CNSanticholinergic effects Anticholinergics can decrease digoxin absorption fromdigoxin tablets

Parameters to Monitor Intraocular pressure monitoring and gonioscope

evalua-tion periodically Monitor for Parkinson’s disease symptoms periodically

Notes Anticholinergic agents are considered useful for the initial treatment of

parkinsonism in patients ≤60 yr with a rest tremor and without akinesia or ity.281,282The drug does not alleviate the symptoms of tardive dyskinesia

rigid-Pharmacology Levodopa is centrally converted to dopamine by DOPA

decar-boxylase and replenishes dopamine, which is deficient in the basal ganglia of tients with Parkinson’s disease Carbidopa, which does not cross the blood–brainbarrier, inhibits peripheral DOPA decarboxylase, thereby increasing the amount

pa-of levodopa available to the brain for conversion to dopamine and limiting eral side effects Addition of carbidopa decreases levodopa-induced nausea andvomiting but does not decrease adverse reactions caused by the central effects oflevodopa.288

periph-Administration and Adult Dosage PO for Parkinson’s disease in patients not receiving levodopa (standard formulation) 25 mg carbidopa/100 mg levodopa

tid initially, increasing in 1 tablet/day increments q 1–2 days to effective dosage,

to a maximum of 8 tablets/day Alternatively, 10 mg carbidopa/100 mg levodopatid or qid initially, to a maximum of 8 tablets/day Initial use of 10 mg car-bidopa/100 mg levodopa can result in more nausea and vomiting because 70–

100 mg/day of carbidopa is needed to saturate peripheral DOPA decarboxylase Ifinitial dosage maximum is reached with 10/100 tablets and further titration is nec-essary, substitute 25 mg carbidopa/250 mg levodopa tid or qid, increasing in 0.5–1 tablet/day increments q 1–2 days to effective dosage, to a maximum of

8 tablets/day Some long-term users with advanced disease might need

>2 g/day.286SR Tab (patients already taking non-SR tablets) start with a dosage

that provides 10% more levodopa daily Initially, divide dosage bid or tid with aninterval of 4–8 hr between doses while awake Ultimately, dosages up to 30%greater might be needed, depending on patient response; (patients not receivingcarbidopa/levodopa) 1 tablet bid initially, at least 6 hr apart, and allow 3 days be-

tween dosage adjustments Usual dosage 2–8 tablets/day If given in combination

with a dopamine agonist or selegiline, lower dosages can be effective

Special Populations Pediatric Dosage (<18 yr) safety and efficacy not

estab-lished

Geriatric Dosage Same as adult dosage.

Dosage Forms Tab 10 mg carbidopa/100 mg levodopa, 25 mg carbidopa/

100 mg levodopa, 25 mg carbidopa/250 mg levodopa; SR Tab 25 mg carbidopa/

100 mg levodopa, 50 mg carbidopa/200 mg levodopa (See Notes.)

Patient Instructions Stopping this medication suddenly can cause Parkinson’s

disease to worsen quickly Report bothersome or unexpected side effects Unlessprescribed, do not take levodopa in addition to this drug Avoid pyridoxine (vita-min B6) if you are taking levodopa alone, although it can be taken with car-bidopa/levodopa Avoid high-protein meals for maximum absorption If you aretaking the sustained-release tablet, swallow a whole or one-half tablet withoutchewing or crushing it Onset of effect of the first morning dose of the sustained-release product could be delayed up to 1 hour compared with the quick-releaseproduct A dark color (red, brown, or black) might appear in saliva, urine, orsweat and can stain clothing

Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is about time for the next dose, take that dose only Donot double the dose or take extra

Pharmacokinetics Onset and Duration Up to 50% of patients experience a

re-duction in efficacy after 5 yr.289(See Notes.)

Fate Carbidopa’s inhibition of peripheral levodopa decarboxylation doubles the

oral bioavailability of levodopa and decreases its clearance by one-half.289–291etary proteins compete with levodopa for intestinal absorption and decrease its ef-fectiveness (Rapid-release 50 mg carbidopa/200 mg levodopa) levodopa bioavail-ability is 99 ± 21% A peak of 3.2 ± 1.1 mg/L occurs in 0.7 ± 0.3 hr.292(SR 50 mgcarbidopa/200 mg levodopa) levodopa bioavailability is 71 ± 24% and increaseswith food A peak of 1.14 ± 0.42 mg/L occurs in 2.4 ± 1.2 hr.292Levodopa Vdis1.09 ± 0.59 L/kg; Cl is 0.28 ± 0.06 L/hr/kg; 90% of clearance is nonrenal.293

Di-t¹⁄₂ (Carbidopa) 2.1 ± 0.6 hr;292(levodopa alone) 1.4 ± 0.3 hr; (levodopa with bidopa) 2 ± 1.3 hr.293

car-Adverse Reactions Anorexia, nausea, vomiting, and involuntary muscle

move-ments (dyskinesias) occur frequently and are generally reversible with dosage duction Occasionally, mental changes, depression, dementia, palpitations, or or-thostatic hypotensive episodes, increased libido, and bullous lesions occur.Rarely, psychosis, hemolytic anemia, leukopenia, or agranulocytosis is reported

re-Compared with levodopa alone, carbidopa/levodopa has markedly reduced GI andcardiovascular side effects However, mental disturbances are not eliminated anddyskinesias can appear earlier in therapy These dyskinesias might require a de-crease in dosage or dosage interval.289,291Side effects can be more pronounced in

patients receiving selegiline or a dopamine agonist as adjunctive therapy.

Contraindications Lactation; nonselective MAO inhibitors concurrently or 2

weeks before carbidopa/levodopa; narrow-angle glaucoma; undiagnosed skin sions; history of melanoma

le-Precautions Pregnancy Use with caution in patients with histories of MI

com-plicated by arrhythmias; peptic ulcer disease; severe cardiovascular, pulmonary,renal, hepatic, or endocrine disease; open-angle glaucoma; bronchial asthma; uri-nary retention; or psychosis Also, use caution in patients receiving antihyperten-sives Symptoms resembling neuroleptic malignant syndrome can occur when car-bidopa/levodopa in combination with other antiparkinson agents is reducedabruptly or discontinued

Drug Interactions Iron salts, including low doses in multivitamins, can decrease

levodopa absorption Other agents for Parkinson’s disease, such as dopamine nists, COMT inhibitors, and selegiline, can increase levodopa side effects whenadded to carbidopa/levodopa Dosage of the levodopa product might need to bereduced by 10–30% Metoclopramide and older neuroleptics (eg, chlorpromazine,haloperidol) have antidopaminergic effects and oppose the action of levodopa.Atypical neuroleptics have less antidopaminergic effect (clozapine has the least)but still can reduce the effectiveness of Parkinson’s disease therapy Cholinergicagents such as tacrine, donepezil, and rivastigmine can worsen Parkinson’s symp-toms by changing the dopamine–acetylcholine balance in the brain Bupropionelicits a higher frequency of side effects in patients taking levodopa Administerbupropion with caution, using small initial doses and small, gradual increases.There are rare reports of adverse reactions, including hypertension and dyskine-sias, resulting from the concomitant use of TCAs and levodopa Isoniazid, pheny-toin, and papaverine can decrease the therapeutic effects of levodopa

ago-Parameters to Monitor Monitor CBC, renal, cardiovascular, and liver functions

periodically during long-term therapy Monitor symptoms of Parkinson’s diseaseperiodically In patients with open-angle glaucoma, monitor intraocular pressure

Notes Levodopa produces sustained improvement in rigidity and bradykinesia in

50–60% of patients.289Tremor is variably affected, and postural stability is sponsive.281,282Loss of therapeutic effect is manifested by fluctuations in motorperformance Patients can experience periods of lack of drug effect (“off” periods)alternating with periods of therapeutic efficacy (“on” periods) Response can bepredictable, where the effect fades before the next dose (“wearing-off” or “end-of-dose”), or unpredictable (“yo-yo”), where there is no relation to the time ofdose.288SR carbidopa/levodopa reduces “off” time an average of 30–40 min/dayand allows a mean 33% reduction in the frequency of administration; the lowerbioavailability of the SR product necessitates a 25% median increase in the dailydosage of levodopa compared with non-SR carbidopa/levodopa.294With diseaseprogression, adjunctive therapy with an MAO-B inhibitor, a dopamine agonist, or

unre-a COMT inhibitor (eg, tolcunre-apone, entunre-acunre-apone) might be required to decreunre-ase thefrequency of fluctuations caused by dyskinesia or dystonia.

Pharmacology Donepezil enhances the action of acetylcholine by reversibly

in-hibiting acetylcholinesterase (AChE), the enzyme responsible for its hydrolysis Ithas a high degree of selectivity for AChE in the CNS, which might explain the rel-ative lack of peripheral side effects Donepezil is indicated for the treatment ofmild to moderate dementia of the Alzheimer’s type No evidence suggests thatdonepezil alters the course of the disease

Administration and Adult Dosage PO for Alzheimer’s disease 5 mg once daily

at bedtime, with or without food The 10 mg dose is associated with a higher quency of side effects but can provide extra benefit in some individuals If a

fre-10 mg dose is desired, first allow 4–6 weeks at 5 mg/day

Special Populations Geriatric Dosage Same as adult dosage.

Other Conditions No dosage adjustment is necessary in patients with renal or

he-patic disease

Dosage Forms Tab 5, 10 mg.

Patient Instructions This drug can be taken with or without food Side effects

can occur when you first start taking donepezil, but these frequently subside after

1 to 2 weeks The maximum benefits of the drug might not occur until 4 to 8 weeksafter starting the drug Because there is variability in the way patients respond todonepezil, decide with your doctor how long to take donepezil Do not abruptlydiscontinue donepezil on your own

Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is about time for the next dose, take that dose only Donot double the dose or take extra

Pharmacokinetics Onset and Duration Onset is in about 3 weeks, with

maxi-mum benefits occurring in 4–8 weeks.295The manufacturer recommends waiting

3 months before evaluating the full effects of the drug.296

Fate Donepezil is completely absorbed and is 96% protein bound Vdss is

12 L/kg; Cl is 0.13 L/hr/kg About 60% is eliminated as hepatic metabolites cluding products of CYP2D6 and CYP3A4 and glucuronides About 17% is ex-creted unchanged in urine.297,298

in-t¹⁄₂ >70 hr.

Adverse Reactions Occasionally, nausea, vomiting, muscle cramps, fatigue,

anorexia, and headache occur

Contraindications Hypersensitivity to donepezil or piperidine derivatives (eg,

biperiden, bupivacaine, methylphenidate, paroxetine, rifabutin, trihexyphenidyl)

Precautions Use with caution in peptic ulcer disease, syncope, sick sinus

syn-drome, bradycardia, altered supraventricular cardiac conduction, asthma, seizures,

or COPD

Drug Interactions There are few in vivo studies In vitro, ketoconazole and

quinidine decrease donepezil metabolism; enzyme inducers might increase its tabolism Although extensively bound to plasma proteins, donepezil does not in-teract with warfarin or furosemide or with cimetidine or digoxin Donepezil canincrease the risk of GI side effects from NSAIDs because of the possible increase

me-in stomach acid production

Parameters to Monitor Monitor mental status and improvements in activities of

daily living initially and then periodically during therapy

Notes Because Alzheimer’s disease is a neurodegenerative disorder, patients

might improve or show no change in their cognitive functions

Pharmacology Bromocriptine and pergolide are ergot-derived dopamine

ago-nists that stimulate dopamine-D2receptors; in addition, pergolide stimulates andbromocriptine partly antagonizes D1receptors Pramipexole and ropinirole arenon–ergot-derived dopamine subtype selective agonists that exert activity in theCNS at D2and D3receptors but have no activity at the D1receptor.299–301D2re-ceptors are thought to play an important role in improving the akinesia, bradykine-sia, rigidity, and gait disturbances of Parkinson’s disease Pramipexole, unlikeother dopamine agonists, binds with 7-fold greater affinity to D3receptors than to

D2receptors and can affect mood Although bromocriptine also can inhibit lactin secretion, it is no longer indicated for the prevention of postpartum lacta-tion Other uses of bromocriptine are the treatment of acromegaly, prolactin-secreting pituitary adenomas, and amenorrhea/galactorrhea secondary to

pro-hyperprolactinemia without a primary tumor (See Dopamine Agonists

Compari-son Chart.)

Administration and Adult Dosage (Bromocriptine) PO for acromegaly

1.25 mg/day or bid with food initially and then increasing in 1.25–2.5 mg/day

in-crements q 3–7 days to a usual maintenance dosage of 2.5 mg bid–tid

Maxi-mum dosage is 100 mg/day PO for hyperprolactinemia 2.5 mg tid PO for

Parkinson’s disease (see Dopamine Agonists Comparison Chart).

Special Populations Pediatric Dosage Safety and efficacy not established PO

for treatment of prolactin-secreting pituitary adenomas (≥11 yr) 1.25–2.5 mgdaily; increase in 2.5 mg/day increments q 2–7 days as tolerated until therapeuticresponse is achieved

Geriatric Dosage Same as adult dosage.

Other Conditions (Pramipexole) adjust for renal impairment as follows: Clcr

35–59 mL/min, give 1.5 mg bid initially, to a maximum of 1.5 mg bid; Clcr15–

34 mL/min, give 0.125 mg/day initially, to a maximum of 1.5 mg/day

Dosage Forms (See Dopamine Agonists Comparison Chart.)

Patient Instructions This medication might improve the symptoms of

Parkin-son’s disease but will not cure it Take this drug with food to minimize stomachupset This drug can cause dizziness, drowsiness, or fainting, especially after thefirst dose Until the extent of these effects is known, use caution when driving, op-erating machinery, or performing tasks requiring mental alertness Mental distur-bances, including vivid dreams, confusion, and paranoid delusions, can occureven with low doses, especially when added to levodopa therapy Avoid concur-rent use of alcohol Inform your physician and pharmacist of any other prescrip-tion or over-the-counter medications you might be taking because these can inter-act with your antiparkinsonian medications Do not abruptly stop taking thismedication or change your dosage without medical supervision (Bromocriptine)women taking this drug to induce ovulation should use a barrier contraceptive.(Pramipexole and ropinirole) some patients have reported sudden excessivedrowsiness, causing them to fall asleep during activities of daily living, includingdriving Notify your doctor immediately if you notice significant daytime drowsi-ness Avoid use of other sedating medications

Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is about time for the next dose, take that dose only Donot double the dose or take extra

Pharmacokinetics Onset and Duration Onset (bromocriptine) 0.5–1 hr;302,303

(pergolide and pramipexole) 1–2 hr; (ropinirole) 1–2 hr on an empty stomach, 3–

4 hr with food.304 Duration (bromocriptine, ropinirole) 3–6 hr; (pergolide,pramipexole) 8–12 hr.305(Bromocriptine in amenorrhea) normal menstrual func-tion usually returns within 6–8 weeks

Fate (Bromocriptine) bioavailability is about 28%; it is 90% bound to plasma

proteins Peak serum concentrations occur in 1.2 ± 0.4 hr, and detectable trations are found for up to 12 hr after discontinuation of drug;302Cl is 4.4 ±2.6 L/hr/kg.303The majority (98%) is excreted in the feces via bile.302(Pergolide)bioavailability is about 60%; it is 90% bound to plasma proteins Approximately40–50% of a dose is excreted in feces over 7 days as at least 10 metabolites.306

concen-(Pramipexole) bioavailability is about 90%; it is 15% bound to plasma proteins

Vdis 7 L/kg; renal Cl is about 0.4 L/hr/kg and markedly exceeds the GFR About90% of a dose is excreted unchanged in urine (Ropinirole) although completelyabsorbed, bioavailability is 55% because of first-pass metabolism It is 36% bound

to plasma proteins and undergoes extensive metabolism in the liver to inactive

metabolites The N-despropyl metabolite is the major metabolite; the drug also is

hydroxylated and glucuronidated

t¹⁄₂ (See Dopamine Agonists Comparison Chart.)

Adverse Reactions Nausea, headache, hallucinations, dyskinesias, somnolence,

vomiting, symptomatic hypotension, dizziness, fatigue, constipation, and headedness occur frequently Occasionally, abdominal cramps and diarrhea occur.(Bromocriptine, pergolide) rarely, hypertension, stroke, seizures, rhinorrhea, orerythromelalgia are reported Pleuropulmonary disease is rare and usually occurs

light-in men, especially light-in smokers receivlight-ing 20–100 mg/day of bromocriptlight-ine for 3–6months; it presents with dyspnea and improves with drug discontinuation.307

Contraindications (Bromocriptine, pergolide) pregnancy; lactation; uncontrolled

hypertension; pre-eclampsia; concurrent use of other ergot alkaloids; tivity to ergot alkaloids

hypersensi-Precautions (Bromocriptine, pergolide) use with caution in patients with

symp-toms of peptic ulcer disease, history of pulmonary disease, MI, liver disease, vere angina, or psychiatric disease (Bromocriptine) use a barrier contraceptiveduring treatment for amenorrhea, galactorrhea, or infertility If pregnancy is de-tected, discontinue the drug (Pramipexole, ropinirole) several patients have re-ported “sleep attacks,” or falling asleep during activities of daily living Thesesudden occasions of sleepiness have resulted in motor vehicle accidents Advisepatients of this possibility and assess them regularly for symptoms of drowsiness.Instruct patients to avoid other sedating medications and drugs that can increaseblood levels of these agents (eg, cimetidine with pramipexole, ciprofloxacin withropinirole) Sudden episodes of falling asleep might necessitate discontinuation ofthe dopamine agonist If pramipexole or ropinirole is continued after such an inci-dent, instruct the patient not to drive or use dangerous machinery

se-Drug Interactions When used with carbidopa/levodopa, it might be necessary to

reduce the dosage of levodopa by as much as 30% to reduce the potential for veloping dyskinesias Drugs that antagonize dopamine (eg, phenothiazines, buty-rophenones, metoclopramide) can reduce the effectiveness of these drugs.(Bromocriptine) erythromycin can increase bromocriptine serum levels.(Bromocriptine, pergolide) other ergot alkaloids can exacerbate cardiotoxic ef-fects (Pramipexole) pramipexole can result in an earlier and higher peak serumlevel of levodopa Drugs that interfere with renal tubular secretion of cations (eg,cimetidine, ranitidine, verapamil, quinidine) can decrease pramipexole renal elim-ination (Ropinirole) ropinirole is metabolized by CYP1A2; therefore, it might in-teract with inhibitors or inducers of this isozyme; ciprofloxacin markedly in-creases AUC and peak serum concentrations Ropinirole might require dosagereduction with co-administration of estrogen

de-Parameters to Monitor Monitor blood pressure frequently during the first few

days of therapy and periodically thereafter Periodically evaluate hepatic,hematopoietic, cardiovascular, and renal function during long-term therapy Mon-itor symptoms of Parkinson’s disease periodically

Notes These drugs can be used as single agents for the treatment of early

Parkin-son’s disease and as adjunctive agents in moderate- to late-stage disease.305,308–312

As first-line agents, dopamine agonists can offer neuroprotection by regulatingdopamine turnover and delaying the introduction of levodopa However, as single

agents, they are less effective than levodopa.

Pharmacology Entacapone is a peripheral acting, selective, and reversible

in-hibitor of COMT, similar in mechanism to tolcapone Entacapone is indicated as

an adjunct to levodopa/carbidopa to treat patients with Parkinson’s disease whoexperience end-of-dose “wearing-off.”313

Administration and Adult Dosage PO for Parkinson’s disease 200 mg, taken

with each levodopa/carbidopa dose, to a maximum of 8 times daily (1600 mg/day)

The 200 mg dose is optimal and is more efficacious than higher doses, possiblybecause of interference with carbidopa absorption at doses ≥400 mg.313

Special Populations Geriatric Dosage Same as adult dosage.

Dosage Forms Tab 200 mg.

Patient Instructions Take one tablet of entacapone with each dose of

levodopa/carbidopa Be aware of the possibility of developing dizziness and potension when rising from a sitting or supine position This effect is more likely

hy-to occur when the drug is first started Nausea is another potential side effect inearly therapy Entacapone can cause a brownish-orange discoloration of the urinethat is harmless Dyskinesias and hallucinations can occur with entacapone, whichcan necessitate the reduction of the carbidopa/levodopa dose Do not drive a car oroperate machinery until you know how entacapone will affect your mental alert-ness or motor abilities

Missed Doses Take this drug at regular intervals If you miss a dose, take it as

soon as you remember If it is close to the time of the next dose, take that doseonly Do not double the dose or take extra

Pharmacokinetics Onset and Duration Onset is rapid and occurs with first dose.

Peak effect is 0.7–1.3 hr after oral administration Entacapone can prolong the fects of a carbidopa/levodopa dose by about 30 min.313

ef-Fate Oral bioavailability 35% Food does not affect entacapone

pharmacokinet-ics, but bioavailability is doubled with liver cirrhosis Peak after a single 200 mgdose is approximately 1.2 g/mL Plasma binding is 98%, mainly to serum albu-min Entacapone does not distribute widely into tissues or CNS; Vdssis 0.4 ±0.16 L/kg Cl is 0.6 ± 0.1 L/kg/hr Entacapone is metabolized almost completelybefore elimination, mainly by isomerization followed by glucuronidation.Metabolites are eliminated primarily by biliary excretion, with 90% of the metab-olized dose found in the feces and 10% in urine Only about 0.2% of the dose iseliminated unchanged in urine.314

t¹⁄₂.  phase 0.4-0.7 hr;  phase 2.4 hr, which accounts for about 10% of the totalAUC

Adverse Reactions Orthostatic hypotension, diarrhea, dyskinesias, and

halluci-nations can occur with entacapone therapy, especially during the initial days oftherapy Dopaminergic side effects, including dyskinesias, nausea, dizziness, hal-lucinations, and insomnia, can occur Dyskinesias are the most common side ef-fect, usually early in therapy Their frequency is reduced with lowering of the lev-odopa/carbidopa dose Diarrhea is a frequent side effect that is mild to moderate in4–10% of patients but severe in 1.3% Orthostatic hypotension, urine discol-oration, abdominal pain, and constipation occur occasionally Elevation of liverenzymes was the same as that with placebo (0.8%) Rarely, rhabdomyolysis, hy-perpyrexia and confusion, resembling neuroleptic malignant syndrome, occur

Contraindications Concurrent use with nonselective MAOIs but it can be taken

with a selective MAO-B inhibitor (eg, selegiline)

Precautions Because 90% of drug elimination is by biliary excretion, use

cau-tion in patients with biliary obstruccau-tion

Drug Interactions Entacapone does not inhibit cytochrome P450 enzymes at

doses used for Parkinson’s disease Despite its extensive protein binding, in vitrostudies have not shown binding displacement between entacapone and otherhighly bound drugs such as warfarin, salicylic acid, and diazepam Drugs that in-terfere with biliary excretion, glucuronidation, and intestinal -glucuronidase,such as probenecid, cholestyramine, erythromycin, ampicillin, rifampin, and chlo-raphenicol, have the potential to interfere with entacapone elimination Drugs thatare metabolized by COMT, such as methyldopa, dobutamine, isoproterenol, andepinephrine, can have enhanced effects when given with entacapone

Parameters to Monitor Monitor symptoms of Parkinson’s disease and excessive

dopaminergic activity The dose of carbidopa/levodopa might need to be reduced

if side effects such as dyskinesias and hallucinations are excessive or intolerable

Pharmacology Galantamine is a competitive, reversible acetylcholinesterase

in-hibitor similar to donepezil and rivastigmine.315,316

Administration and Adult Dosage PO for Alzheimer’s disease 4 mg bid

ini-tially with a meal, increasing in 4 mg bid increments at 4-week intervals to a mum of 12 mg bid In moderate hepatic or renal dysfunction the maximum dosage

maxi-is 8 mg bid Avoid in severe hepatic (Child-Pugh 10–15) or renal (Clcr<9 mL/min)impairment If more than a few days of therapy are missed, resume therapy at

4 mg bid

Dosage Forms Tab 4, 8, 12 mg.

Pharmacokinetics Oral bioavailability is ≥90%; food decreases peak tion and rate, but not extent of absorption Peak cholinesterase inhibition occurs

concentra-1 hr after a dose It is concentra-18% plasma protein bound and distributed extensively intoRBCs Vdssis 2.6 L/kg; Cl is 0.34 L/hr/kg Metabolism is primarily by CYP2D6and 3A4 About 20–25% is excreted unchanged in urine in 24 hr Half-life is 5–7 hr.315

Adverse Reactions GI side effects (eg, nausea, vomiting, diarrhea, anorexia,

weight loss), are most prominent during dosage escalation Dizziness, headache,chest pain, tremor, depression, rhinitis, urinary incontinence, flatulence and brady-cardia also occur frequently Various cardiac arrhythmias, increased alkalinephosphatase, thrombocytopenia, GI bleeding, hyperglycemia, and psychiatricsymptoms occur occasionally Esophageal perforation has been reported

Pharmacology In the treatment of amyotrophic lateral sclerosis, riluzole is

hy-pothesized to protect motor neurons from degeneration and death Although theexact mechanism of action is unknown, there are three pharmacologic properties

of the drug that are thought to be relevant: inhibition of glutamate release, vation of voltage-dependent sodium channels, and interference with intracellularevents that follow activation of excitatory amino acid receptors

inacti-Administration and Adult Dosage PO for amyotrophic lateral sclerosis 50 mg