Lecture Math for the pharmacy technician Concepts and calculations Chapter 10 – Lynn M. Egler, Kathryn A. Booth

Chapter 10, Pediatric and geriatric considerations. This chapter includes drug.orders based upon body weight. It introduces body surface area (BSA).calculations. Discussions of special concerns for pediatric and geriatric.patients are also presented.

Chapter 10: Pediatric and Geriatric Considerations

Egler • Booth

Considerations

 Explain why dosages calculations for

specific populations must be based on the individual patient.

 Identify factors that affect the

absorption, distribution,

biotransformation, and elimination of

drugs in special populations.

 Determine safe doses for special

population patients.

When you have successfully completed Chapter 10, you

will have mastered skills to be able to:

Learning Objectives (con’t)

 Determine safe doses for special

 Find a patient’s body surface area

(BSA)

 Calculate patient dosages based on a

patient’s BSA

 Two special populations require extra

consideration when calculating

medication dosages

 Pediatric (children under age 18)

 Geriatric (mature adults over age 65)

 Risk of harm is far greater due to

way they break down and absorb

 Clarify all confusing drug orders

 Calculate with absolute accuracy

 Verify that dose is safe

 Seek assistance from your

supervisor

Do not take short cuts with

medication calculations

Factors that Impact Dosing

 Normal dose of medication makes

assumptions

 About the patient’s body and age

 That body systems are fully developed

and functioning

 Special populations may need

dosages adjusted due to this

 Study of how drugs are used by the

Understanding these processes allows

for adjustments for special

populations

Absorption

 Process that moves a drug from the

site where it is given into the

bloodstream

 IV medications bypass the absorption

process by going directly into the bloodstream

 Oral medications absorbed in digestive

system

 Process that moves the drug from

the bloodstream to other body

tissues and fluids

 Target site is where the drug

product produces its desired effect

 Each drug affects drug target sites

Biotransformation

 Process that chemically changes the

drug in the body

 Occurs primarily in the liver

 Helps to protect the body from

foreign chemicals including drugs

 Process where the drug leaves the

Drug Adjustment

 Adjustment is needed if one of these four

processes are not functioning within

certain limits.

 Dose adjustment is made according to

nature and severity of patient’s condition.

 You are not expected to make these

adjustments, but be aware that they may have to be done.

Functions of body systems change over

the life of a person

Newborns – systems not developed yet

 pH of stomach is lower

 Thinner skin

 Liver still developing

 Less circulation to muscles

Geriatrics – systems begin to

deteriorate

 Skin and veins become fragile

 Decreased liver function

 Decreased kidney function

 Poor circulation

 Other Considerations

 Parent or caretaker may be

administering or assisting them with medications

 These individuals will need

education regarding any regular

or special requirements

Caretaker About Medications

1. Name of the medication

7 Required follow-up tests, doctor

appointments

8 Possible side effects and what to do

9 Interactions with other drugs and

foods

10 Symptoms to report to the doctor

11 What to do if a dose is missed

12 Keeping a list of all medications

Ensuring Safe Dosages

 When you are working with special

populations, always check the package

insert, drug label, or product literature to ensure the safety of the dose to be

administered.

 Drug orders may be written in several

ways If you measure the medication, you have the responsibility to check whether the dose is the standard recommended

 The recommended dose is sometimes

written as a range, with a minimum and a maximum recommended dose

In this case, you will need to

determine if the dose ordered is not less than the minimum or greater

than the maximum recommended

dose

Ensuring Safe Dosages (con’t)

Determine whether the following order is

safe If safe, calculate the amount to

Convert ounces carefully.

 The weight of babies is often measured in

pounds and ounces.

 Because 16 oz = 1 lb, an ounce is not a

tenth of a pound.

 A baby who weighs 8 lb 6 oz does not

weigh 8.6 lb.

CAUTION! (con’t)

Convert 6 ounces

to pounds using

as the conversionoz

16 1 lb

lb

0.375 oz

16 1 lb oz

Calculating dosage based on body weight:

1 Convert the patient’s weight to kilograms

2 Calculate the desired dose, D, by

multiplying dose ordered by the weight in kilograms such as

dose

desired kg

or dose

desired

kg

kg

mcg x

kg

mg

Weight (con’t)

3 Confirm whether or not the desired

dose is safe by checking the label, package insert, or product

literature If unsafe, consult the physician who wrote the order

4 Calculate the amount to

administer, using fraction proportion, ratio proportion, dimensional analysis, or the

Calculate the amount to administer to a year-old who weighs 34 lb.

three-Ordered: hysocyamine sulfate 5 mcg/kg subq

1 h pre-anesthesia

On hand: hysocyamine sulfate 0.5 mg/mL

Answer: 0.15 mL

Calculations

 There are two other forms of

calculations used to calculate

pediatric doses, Clark’s Rule and

Young’s Rule

 Clark’s Rule uses the weight of the

child to determine the desired dose and

 Young’s Rule uses the age of the child

to determine the desired dose.

 Memory Tip

 Young = age; the word “young”

refers to the age of an individual, and Young’s Rule uses the age of the child

to determine the desired dose

Calculations (con’t)

 Clark’s Rule for children’s dosage

calculations uses the following formula:

Child's weight in pounds

× average adult dose = pediatric patient's dose

150 pounds

Using Clark’s Rule, find the amount to

be dispensed The patient is a old child who weighs 50 lb; the

6-year-average adult dose is 250 mg

mg

mg lb

lb

3 83

250 150

50

=

×

Calculations (con’t)

 Young’s Rule for children’s dosage

calculations uses the following formula (this formula can be used only if the child is a least 1 year of age):

dose s

patient' pediatric

dose adult

average years

12 years

in age s

child'

years in

age s

child'

=

× +

Using Young’s Rule, find the amount to

be dispensed The patient is a old child who weighs 50 lb; the

6-year-average adult dose is 250 mg

mg

mg years

years

years

3.83

25012

6

6

=

×+

Surface Area (BSA)

 BSA calculations are used to provide

more accurate dosage calculations specific to the patient’s size and

severity of his/her illness

 Some medications are based on

patient’s body weight only

 Both weight and height are used to

determine a patient’s body surface

 A patient’s BSA is stated in square

meters or m2

 To calculate the BSA you must know

the height and weight

 Use a formula or a special chart

called a nomogram

(kg) weight

(cm) height

2 If you know the height in

inches and weight in pounds, calculate

2

m

3131 weight (lb)

(in) height

Find the body surface area for an adult who

is 5’6” tall and who weighs 168 lb.

BSA = 1.9 m2

 Using a straight edge, align the

straight edge so it intersects at the height and weight

 Doing so will create an intersection

in the BSA scale

a Nomogram (con’t)

Find the body surface for a

baby who is 24 in and

weighs 14 lb and 8 oz

Use the “Child’s

Nomogram”

BSA = 0.21 m2

Calculating dosage based on BSA:

1 Calculate the patient’s BSA.

2 Calculate the desired dose:

dosage ordered x BSA = desired dose

3 Confirm whether or not the desired dose is

safe If unsafe, consult the physician who wrote the order.

4 Calculate the amount to administer,

using fraction proportions, ratio

proportions, or the formula method.

Calculating Dosage Based on BSA (con’t)

Ordered: Ceenu (1st dose) 140 mg now

for a child whose height is 38 in and weight is 47 lb

According to the package the first dose

is a single oral dose providing 130 mg/m2

True or False

A baby who weighs 6 lb 8 oz

weighs 6.8 lb.

Answer: False

Review and Practice

Answer: True

True or False

A baby who weighs 9.5 lb

weighs 9 lb 8 oz.

What two things are pediatric dosages

often based on?

Answer: Weight and BSA

THE END

No matter how rushed you may feel,

you cannot take shortcuts with any

medication calculations, especially

patients from special populations.