The influence of food on the pharmacokinetics of piperaquine in healthy Vietnamese volunteers

The aim of this study was to determine the influence of a standard Vietnamese meal on the single-dose pharmacokinetics of piperaquine when administered in combination with dihydroartemis

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Acta Tropica

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / a c t a t r o p i c a

The influence of food on the pharmacokinetics of piperaquine in healthy

Vietnamese volunteers

Trinh Ngoc Haia,1, Sofia Friberg Hietalab,1, Nguyen Van Huonga, Michael Ashtonb,∗

aPharmaceutical Unit, Department of Malaria Treatment and Research, National Institute of Malariology, Parasitology and Entomology (NIMPE),

BC10200 Tu liem, Hanoi, Viet Nam

bUnit for Pharmacokinetics and Drug Metabolism, Institute of Neuroscience and Physiology, Sahlgrenska Academy at G¨ oteborg University,

Box 431, 405 30 G¨ oteborg, Sweden

a r t i c l e i n f o

Article history:

Received 5 November 2007

Received in revised form 16 May 2008

Accepted 19 May 2008

Available online 24 May 2008

Keywords:

Malaria

Piperaquine

Food–drug interactions

Pharmacokinetics

a b s t r a c t

The combination piperaquine and dihydroartemisinin is emerging as first line treatment of uncomplicated falciparum malaria in Southeast Asia The aim of this study was to determine the influence of a standard Vietnamese meal on the single-dose pharmacokinetics of piperaquine when administered in combination with dihydroartemisinin, and to gain extended data on the terminal half-life of piperaquine in healthy Vietnamese volunteers

Subjects were randomly assigned to take a single oral dose of piperaquine phosphate

(640 mg) + dihydroartemisinin (80 mg) together with a standardized Vietnamese meal (n = 16) or to remain fasting for 4 h following drug intake (n = 16) Frequent blood sampling was conducted during 36 h,

fol-lowed by weekly samples for 7 weeks The pharmacokinetic parameters of piperaquine were determined

by noncompartmental analysis

The median (80% central range) AUC0–lastwas 11.5 (6.9–17.3) h mg/L in fed and 13.9 (2.8–19.3) h mg/L in fasting subjects, indicating a considerable variability in exposure in both groups The estimated overall oral clearance was 0.27 (0.12–1.49) L/(h kg), the volume of distribution during the terminal elimination phase was 230 (102–419) L/kg and estimated terminal half-life was 18 (5–93) days This study did not demonstrate a significant impact of a standardized Vietnamese meal on the oral absorption of piperaquine

© 2008 Elsevier B.V All rights reserved

1 Introduction

The combination piperaquine (PQ) phosphate and

dihy-droartemisinin (DHA), is first line treatment of uncomplicated

falciparum malaria in Vietnam The current dose regimen in

Viet-nam is two tablets, each containing 320 mg PQ phosphate and

40 mg DHA, administered at 0, 6, 24 and 36 or 48 h The efficacy

and safety of this PQ + DHA combination treatment has been

estab-lished in a number of studies (Denis et al., 2002; Karunajeewa et

al., 2004; Tran et al., 2004) The same total dose administered in a

once daily regimen for 3 days is also highly effective (Ashley et al.,

2005; Tangpukdee et al., 2005; Mayxay et al., 2006; Smithuis et al.,

2006; Hasugian et al., 2007; Ratcliff et al., 2007)

Despite increasing clinical use, the pharmacokinetics of PQ have

only recently been described, in healthy subjects as well as in

adult and pediatric patients (Hung et al., 2004; Roshammar et al.,

∗ Corresponding author Tel.: +46 31 786 34 12; fax: +46 31 786 32 84.

E-mail address:Michael.Ashton@pharm.gu.se (M Ashton).

1 These authors contributed equally to the work.

2006; Ahmed et al., 2008; Karunajeewa et al., 2008; Tarning et al., 2008) The absorption of PQ has been shown to be discontin-uous with plasma profiles exhibiting multiple peaks (Sim et al., 2005; Roshammar et al., 2006; Ahmed et al., 2008) PQ disposi-tion is characterized by a multiphasic profile with an excepdisposi-tionally slow terminal elimination during which the half-life may exceed

1 month in the adult (Tarning et al., 2005) Average oral clearance

(CL/F) values between 0.9 and 1.4 L/(h kg) and volume of

distribu-tion values between 103 and 716 L/kg have been reported (Hung et al., 2004; Roshammar et al., 2006; Ahmed et al., 2008; Tarning et al., 2008)

PQ is a highly lipophilic base, with a water/octanol partition

(log P) as high as 6.11 (Warhurst et al., 2007) Combining PQ with a high-fat meal resulted in a twofold increase of the AUC as well as

a marked increase in maximum concentrations (Cmax) (Sim et al.,

2005) The fatty food intake did not appear to alter the time to reach

Cmax, or influence the frequency of multiple peaks in the plasma concentration of PQ The clinical implication of an increased AUC due to food intake is unclear It has been proposed that an increased exposure due to better absorption with food may cause a greater risk for side effects rather than increase efficacy (Sim et al., 2005) 0001-706X/$ – see front matter © 2008 Elsevier B.V All rights reserved.

T.N Hai et al / Acta Tropica 107 (2008) 145–149

The aim of this study was to determine the influence of a

standard Vietnamese meal on the pharmacokinetics of PQ when

administered in combination with DHA, and to further explore the

terminal elimination half-life of PQ in healthy Vietnamese

volun-teers

2 Method

2.1 Subjects and study design

Thirty-two healthy Vietnamese adult subjects were included in

the study The number of subjects was calculated to have an 80%

power to detect a difference in mean AUCs equal to, or greater

than, one standard deviation Subjects were included if they were

healthy according to a physical examination including a resting

electrocardiogram, blood pressure and heart rate measurement,

standard biochemistry (total bilirubin, creatinine, AST, ALT,

erythro-cytes, hemoglobin and leucocytes) and medical history Subjects

were excluded if they had a history of antimalarial intake within 3

months prior to inclusion, had known allergies to the study drugs or

excipients, were pregnant or planning to become pregnant within

6 months

Following an overnight fast subjects received two tablets of

CV.Artecan (Pharmaceutical Company 26, Ho Chi Minh City,

Viet-nam), each containing 40 mg DHA and 320 mg PQ phosphate

(equivalent of 171.5 mg of PQ base) as a single dose under

super-vision of study personnel Subjects were randomly assigned to take

the study drugs together with a standardized Vietnamese meal

(n = 16) or to remain fasting for another 4 h following drug intake

(n = 16) The meal consisted of one fried egg and a meat soup (pork,

beef, rice, vegetables and beans) and contained approximately

482 kcal (17 g fat, 27 g protein and 53 g carbohydrates) This meal

represents approximately one-fourth of the average daily caloric

intake in the adult Vietnamese population (Thang and Popkin,

2004) Blood samples were obtained through an indwelling venous

catheter at −5 min (pre-dose), 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10,

11, 12, 24, 28, 32 and 36 h and by venepuncture in the

morn-ings on days 7, 14, 21, 28, 35, 42 and 49 Blood samples were

drawn into heparinized Vacutainer® tubes which were inverted

ten times by hand and centrifuged for 5 min at 3000 × g Plasma

aliquots were transferred to plastic cryotubes (Nunc, Hereford,

UK) and frozen at −70◦C until transported in dry ice for analysis

at G ¨oteborg University The safety of the treatment was assessed

with a questionnaire completed on days 1, 2, 7, 14, 21, 35 and

49

The study was conducted in accordance with the principles laid

down in the Helsinki declaration and the standards established for

Good Clinical Practice (GCP) at the Clinical Unit of the National

Insti-tute of Malariology, Parasitology and Entomology (NIMPE) in Hanoi,

Vietnam Study approval was obtained from the Ethics and Human

Research Committee at NIMPE and from the Ministry of Health,

Vietnam

2.2 Chemical assay

PQ plasma concentrations were determined using a previously

described method (Lindegardh et al., 2005) In brief: PQ was

sepa-rated from plasma components using solid-phase extraction (MPC

solid-phase extraction 96-well plates, Millipore AB, Solna, Sweden)

followed by concentration determination using HPLC (Chromolith

Performance column, Chromtech AB, H ¨agersten, Sweden) with UV

detection at 347 nm Detector response (peak heights) and

nomi-nal plasma concentrations were log-transformed to generate linear

calibration curves (range 5–5000 ␮g/L) The inter-day coefficient of

variation (CV) in quality control samples was 13%, 14% and 14% and the intra-day accuracy, expressed as mean percentage of nominal

value, was 110% (n = 4), 107% (n = 4) and 92% (n = 5) at 20, 198 and

1235 ␮g/L, respectively The lower limit of quantification (LLOQ) was set at 5 ␮g/L with an intra-day CV of 14%, and an accuracy of

96% (n = 5) All concentrations are expressed in terms of PQ base.

2.3 Pharmacokinetic and statistical analysis

The pharmacokinetic parameters of PQ were determined by noncompartmental analysis in WinNonlin version 5 (Pharsight Cor-poration, California, USA) The area under the concentration–time curve (AUC) was calculated using linear interpolation between increasing concentrations and logarithmic interpolation between declining concentrations

The AUC0–lastwas defined as the area under the concentration time curve from the time of dose until the last measurable con-centration above LLOQ The AUClast–∞was extrapolated from the predicted concentration at the time of the last concentration above the LLOQ (AUClast–∞= Cpred/z) The terminal elimination constant,

z, was determined from the slope of on average five sampling points (range 3–7) The mean percentage of the AUC0–∞ extrapo-lated beyond the last sample above LLOQ was 37% and ranged from 7% to 90% The poor description of the AUClast–∞was caused by the very slow terminal elimination in some subjects

The median and the 80% central range of the pharmacoki-netic parameters were calculated in Microsoft Excel (Microsoft Corporation, Washington, USA) The estimated pharmacokinetic parameters for the fed and the fasting state were compared using the Mann–Whitney two sample rank-sum test in SPSS 12.0.1 for Windows (SPSS Inc., Illinois, USA)

3 Results

The demographic profiles did not differ between the two study groups Median (range) age was 26 (19–45) and 31 (19–56) years and the body mass index was 21 (18–26) and 22 (17–25) kg/m2

in fed and fasting subjects, respectively The male:female ratio was 13:3 in fed and 14:2 in fasting subjects The mean (range) bodyweight normalized dose was 6.00 (4.90–7.46) and 6.02 (4.64–7.15) mg PQ base/kg in fed and fasting subjects, respectively All subjects complied with the study schedule and there were no adverse effects reported in either study group during clinic stay or during the 49 days of follow-up

(6.9–17.3) h mg/L in fed and 13.9 (2.8–19.3) h mg/L in fasting subjects There was a considerable interindividual variability in exposure as shown by the approximately 20-fold range (max–min)

in AUC0–lastin both groups There was less variability in AUC0–24, i.e early exposure, which had a range of 3 and 4 h mg/L in fed and fasting subjects, respectively Median (80% central range) AUC0–24was 2.2 (1.4–3.6) h mg/L in fed and 1.7 (0.7–3.6) h mg/L in fasting subjects No statistically significant difference in exposure between fed and fasting subjects was observed (Table 1)

As indicated inFig 1, piperaquine elimination was marked by a very slow terminal phase in many subjects The estimated overall

median (80% central range) CL/F was 0.27 (0.12–1.49) L/(h kg), cor-responding values for V z /F andt1/2zwere 230 (102–419) L/kg and

18 (5–93) days

Multiple peaks were a prominent feature of the PQ concentration–time profiles in both fasting and fed subjects, occurring in 26 out of the 32 individuals

T.N Hai et al / Acta Tropica 107 (2008) 145–149

Table 1

Piperaquine pharmacokinetic parameters for fed and fasting healthy subjects after an oral single dose of piperaquine phosphate and dihydroartemisinin determined by noncompartmental analysis

4 Discussion

This study did not show a significant impact of a standardized

Vietnamese meal on the pharmacokinetics of PQ The

interindivid-ual variability in exposure was considerable as shown by the 20-fold

range in AUC0–lastin both fed and fasting subjects The multiple

peaks described in previous studies (Sim et al., 2005; Roshammar

et al., 2006; Ahmed et al., 2008) occurred in both groups

Given the long elimination half-life, a parallel group design was

chosen as recommended by the FDA (CDER, 2003) The number of

subjects required was calculated based on the assumption that a

clinically relevant difference in AUCs would be greater than one

standard deviation Our study showed a major interindividual

dif-ference in AUC0–lastwith CVs of 40% and 53% for fed and fasting

subjects, respectively Thus the between-group difference would

have had to be around 50% to be identified as statistically significant

in this study

Sim et al (2005)found a twofold increase in PQ exposure

fol-lowing intake with a high-fat meal They proposed that the risk

of side effects may increase if PQ is administered with food.Sim

et al (2005)used a high-fat (37 g) test meal as recommended by the FDA, designed to achieve the maximum effect on GI physiol-ogy and systemic drug availability In contrast, our study meal, as the normal Vietnamese diet, contained considerably less fat Our results indicate that there is no increased risk of adverse effects due to concomitant low-fat food intake during treatment with PQ

There are three published studies describing the pharmacoki-netics of PQ following a single oral dose in healthy subjects (Sim et al., 2005; Liu et al., 2007; Ahmed et al., 2008) The dose-normalized total exposure in fasting subjects (AUC0–∞) was approximately three times greater in our study compared to studies by Sim et al (2005) and Ahmed et al (2008) (based

on geometric mean values) but only half of that described by Liu et al (2007) (arithmetic mean) In keeping with the dif-ferences in AUC0–∞ the estimated CL/F varies between studies, with ours being approximately one-third of the CL/F reported

bySim et al (2005)and Ahmed et al (2008) Liu et al (2007)

report a mean CL/F of 0.02–0.03 L/(h kg) following a single dose

of PQ However, using their reported mean AUC0–∞ a much

Fig 1 Piperaquine plasma concentrations over time following a single-oral dose of piperaquine phosphate and dihydroartemisinin in fed (panel A, n = 16) and fasting healthy

T.N Hai et al / Acta Tropica 107 (2008) 145–149 higher CL/F of approximately 0.1–0.2 L/(h kg) can be calculated

(CL/F = dose/AUC0–∞), suggesting some caution when evaluating

these results

Different drug products were used in these studies and it is

possible that differences in drug formulation significantly

influ-enced the bioavailability of PQ A relatively small change in the

fraction of dose absorbed, from, e.g 10% to 20%, would result in

a doubling of the AUC0–∞and a halving of the CL/F Further, the

ethnicities and gender distribution of the study populations

dif-fered The studies bySim et al (2005)andAhmed et al (2008)

were both conducted in Caucasian volunteers.Liu et al (2007)

stud-ied Chinese volunteers while the current study was conducted in

a Vietnamese population.Liu et al (2007)suggest a gender

differ-ence in pharmacokinetics, with a significantly higher AUC0–∞in

female subjects which appeared to hold true also for dose per body

weight normalized AUCs However, the relevance of the reported

normalizations for all other pharmacokinetic parameters, except

Cmax, is unclear.Sim et al (2005)had an equal but small number of

male and female subjects (4/4), also in the current study, with only

5/32 subjects being female, the number was too small too justify a

separate analysis.Ahmed et al (2008)did not include any female

subjects

Values for CL/F (Table 1) indicate PQ to be a drug of low organ

extraction (maximal extraction = (CL/F)/organ blood flow ≤ 0.3) In

the rat, renal clearance of PQ was found to be negligible with a

fraction excreted as unchanged drug less than 1% after intravenous

administration (Tarning et al., 2007) Assuming that non-renal

elimination predominates also in human beings the hepatic

extrac-tion can therefore be assumed to be about or less than 30%

depending on the value of absolute bioavailability (F) The low organ

extraction suggests the oral bioavailability of PQ to depend on

sol-ubility in the gastrointestinal tract rather than any major first-pass

metabolism

Together with a remarkably large volume of distribution, the low

extraction results in an elimination half-life of substantial length

Earlier studies have reported a long and variable elimination of PQ

with mean half-lives of 11–33 days (Hung et al., 2004; Sim et al.,

2005; Tarning et al., 2005; Roshammar et al., 2006; Ahmed et al.,

2008) The present study confirms the presence of a prolonged

elimination phase The estimated median half-life was 18 days

Obviously, individual half-lives longer than the duration of

sam-pling were estimated with poor accuracy Nevertheless, these PQ

concentrations sustained on a 20–50 ␮g/L level may contribute to

a post-treatment prophylactic effect (Tarning et al., 2008) lasting

several weeks

Although there have been attempts to model the multiple

peak kinetics of PQ (Roshammar et al., 2006), their presence

lend non-compartmental analysis suitable for rich data

Multi-ple peaks occurring within hours of drug intake could be the

result of erratic dissolution and/or absorption regulated by

gas-tric emptying since two tablets were administered It could

also result from precipitation and slow re-dissolution as the

lipophilic base passes from the acidic environment of the

stom-ach to the more alkaline small intestine However, as indicated

in Fig 1, PQ concentrations continued to oscillate during the

whole study period The multiple peaks have been suggested

to result from enterohepatic recirculation of PQ (Sim et al.,

2005) However, results in the rat suggest that biliary excretion

of PQ is quantitatively too low (<1%) to account for

enterohep-atic circulation affecting its in vivo disposition (Tarning et al.,

2007)

The current study shows that there is considerable variability in

PQ exposure following a single oral dose in healthy adult subjects

Concomitant food intake did not markedly influence the

pharma-cokinetics of PQ under the study conditions

Acknowledgements

The kind assistance of Professor Le Khanh Thuan, Director of NIMPE, is gratefully acknowledged The authors are also thankful

to Frida Gillberg for initial protocol development

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