Eur J Clin Pharmacol (2006) 62: 335–341 DOI 10.1007/s00228-005-0084-9 CLINICAL TRIALS Daniel Röshammar Trinh Ngoc Hai Sofia Friberg Hietala Nguyen Van Huong Michael Ashton Pharmacokinetics of piperaquine after repeated oral administration of the antimalarial combination CV8 in 12 healthy male subjects Received: 17 June 2005 / Accepted: 21 November 2005 / Published online: 29 March 2006 # Springer-Verlag 2006 Abstract Objective: To investigate the pharmacokinetic properties of piperaquine after repeated oral administration of the antimalarial combination CV8 in healthy subjects Methods: Twelve healthy fasted Vietnamese males were administered four tablets CV8 (320 mg piperaquine phosphate, 32 mg dihydroartemisinin, mg primaquine phosphate, 90 mg trimethoprim) on day 1, followed by two tablets every 24th hour, for a total of days Blood samples were frequently drawn on days and and sparsely drawn until day 29 Samples were analyzed for piperaquine using solid phase extraction followed by high-performance liquid chromatography Population pharmacokinetic parameter estimates were obtained by nonlinear mixed effects modeling of the observed data using NONMEM Results: A two-compartment disposition model with an absorption lag time described the observed piperaquine concentrations Absorption profiles were found to be irregular with double or multiple peaks A dual pathway first-order absorption model improved the goodness of fit Piperaquine pharmacokinetics were characterized by a large volume of distribution and a terminal half-life of several days Estimates [95% confidence interval (CI)] of CL/F, Vss/F and t½z were found to be 56.4 (29–84) l/h, 6,000 (3,500–8,500) l and 11.7 (8.3–15.7) days, respectively Conclusion: Piperaquine pharmacokinetics after repeated oral doses were characterized by multiple concentration peaks and multiphasic disposition, resulting in a long terminal half-life Sustained exposure to the drug after treatment should be taken into account when designing future clinical studies, D Röshammar S Friberg-Hietala M Ashton (*) Unit for Pharmacokinetics and Drug Metabolism, Department of Pharmacology, Sahlgrenska Academy at Göteborg University, Box 431, 405 30 Göteborg, Sweden e-mail: Michael.Ashton@pharm.gu.se Tel.: +46-3177-33412 Fax: +46-3177-33284 T N Hai N V Huong National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam e.g duration of follow-up, and may also drive resistance development in areas of high malaria transmission Introduction With the spread of multidrug-resistant falciparum malaria, the need for new treatment options is great Piperaquine, (1, -bis-[1-(-7-chloroquinolyl-4)-piperazinyl-1]-propane) phosphate (Fig 1), was first synthesized at Rhône-Poulenc in the 1960s and was later developed at the Shanghai Research Institute of Pharmaceutical Industry [1] In 1978 piperaquine replaced chloroquine as first-line treatment in southern PR China and was for a decade widely used both for prophylaxis and treatment, until its use diminished on behalf of new therapies and emerging drug resistance Interest in piperaquine has recently been renewed, now in combination treatment partnered with peroxide antimalarials [2] If resistance mechanisms are not linked, the use of a combination treatment of differently acting malaria drugs could diminish the spread of resistance development among the malaria parasites [3, 4] Treatment regimens of long-acting drugs, such as piperaquine, in combination with the potent artemisinin derivates are currently recommended by the WHO [5, 6] A piperaquine-dihydroartemisinin co-formulation (Artekin) was found to be highly efficacious with an acceptable safety profile in studies to date [7–10] A piperaquine-dihydroartemisinin-trimethoprim combination (Artecom) was likewise effective [11] A fixed dose piperaquine-dihydroartemisinin-trimethoprimprimaquine combination (CV8) was found to be an effective combination against multidrug-resistant falciparum malaria at a low price [12] and has in recent years been extensively used in Vietnam Current dose regimens are empirically based rather than built on a sound understanding of the pharmacokinetics and pharmacodynamics of the combined drugs Despite its clinical use, there is limited information on the pharmacokinetics of piperaquine A study in mice suggested a piperaquine half-life of about days in this species 336 Fig Chemical structure of piperaquine phosphate [13] In humans, the first and hitherto only reports described the effects of a high-fat meal on the relative oral bioavailability of piperaquine [14] and the population pharmacokinetics in adults and children with uncomplicated malaria treated with Artekin [15] Piperaquine population pharmacokinetics were described by a twocompartment model resulting in estimates of the terminal half-life (t½z) of 23 days in adults and 14 days in children In this present study we report the clinical pharmacokinetics of piperaquine in fasted healthy Vietnamese subjects after multiple oral administration of CV8 To estimate relevant pharmacokinetic parameters, including their intersubject and between-occasion variability, we chose a population pharmacokinetic modeling approach Methods Subjects and study design Twelve Vietnamese healthy male subjects between 21 and 45 years old, with a mean (SD) age of 31 (3.5) and a mean body weight of 58 (13) kg, were included in the study after providing their signed informed consent to participate The study was conducted in 2001, in accordance with the Helsinki declaration and the standards established for Good Clinical Practice (GCP) at the Clinical Unit of the National Institute of Malariology, Parasitology and Entomology (NIMPE) in Hanoi, Vietnam Approval of the study was given by the Vietnamese Ministry of Health and by the WHO Secretariat Committee for Research Involving Human Subjects (SCRIHS) Subjects were judged to be healthy on the basis of their medical history, a normal electrocardiogram (ECG), normal haematology laboratory tests, normal liver and renal function tests and on the basis of a physical examination Subjects with presence of acute or chronic infection, hepatic, renal or gastrointestinal disorder, glucose-6-phosphate dehydrogenase (G6PD) deficiency, intolerance to antifolate drugs, presence of malaria parasites on a thick smear, heavy smoking habits, abuse of alcohol or other drugs, or subjects likely to violate the protocol were excluded No history of antimalarial ingestion (piperaquine, artemisinin and its derivates, chloroquine, amodiaquine, quinine, halofantrine or pyrimethamine-sulfadoxine) within the preceding weeks was allowed, as well as any drug intake within weeks prior to or during the study Subjects were administered four tablets of CV8 orally as a single dose on day (6-8 a.m.) followed by two tablets in the mornings of days and 3, respectively, with a fixed dose interval of 24 h Doses were given after an overnight fast (no food or liquids from 10 p.m.) with a glass of water (250 ml) under supervision of assigned study personnel A standardized meal (rice noodle soup with beef) was served all subjects h after the dose The CV8 tablets contained piperaquine phosphate 320 mg, dihydroartemisinin 32 mg, primaquine phosphate mg, trimethoprim 90 mg (Pharmaceutical Factory No 26, Ho Chi Minh City) Nine tablets from the study batch were readily and separately dissolved in 250 ml 0.05 M phosphoric acid Piperaquine contents were evaluated against four reference solutions (each containing 320 mg piperaquine phosphate in 250 ml 0.05 M phosphoric acid) Aliquots from each solution were analyzed for piperaquine contents by high-performance liquid chromatography (HPLC) (vide infra) by direct injection after dilution with mobile phase The mean (% CV) piperaquine phosphate content was 320 mg (1.1) in the reference solutions and 332.8 mg (2.2) in the tablets, corresponding to 104% of the label content Subjects were detained at the clinic days and On day subjects were monitored for changes from pretreatment in clinical safety (ECG readings), haematology (full blood counts and B-haemoglobin), blood chemistry (plasma aspartate aminotransferase, alanine aminotransferase, bilirubin, creatinine and blood urea nitrogen), blood pressure, body temperature and other vital changes The occurrence of adverse events was actively investigated by interviews (open question followed by directed organ-related questions) on day and the final visit on day 29 Blood sampling Venous blood samples (5 ml) were collected pre-dose and at 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10, 12, 24, 48, 48.25, 48.5, 48.75, 49, 49.5, 50, 50.5, 51, 52, 53, 54, 56, 58, 60, 72, 96, 120, 144, 168, 240, 360, 528 and 696 h after the first dose Samples were drawn via an indwelling forearm catheter (Venflon, 1.3×30 mm) over the first 12 h on days and in order to obtain complete concentrationtime profiles after the first and last doses and at other sampling times by venepuncture Blood samples were drawn into heparinized Vacutainer tubes which were inverted ten times by hand and centrifuged for at 3,000 g Plasma aliquots were transferred to plastic cryotubes (Nunc, Hereford, UK) and frozen at –70°C until transported in dry ice for quantitation of piperaquine at Göteborg University within months after collection Chemical assay Piperaquine in plasma was quantitated by solid phase extraction (SPE) followed by a HPLC method with UV detection as previously described [16] but with some modifications The SPE column used was a ml C18- 337 column (International Sorbent Technology Ltd, Mid Glamorgan, UK) The chromatographic system comprised a LC-10ADVP pump (Shimadzu, Kyoto, Japan), Midas injector (Spark, Holland) and a Chromolith Performance RP-18e (100×4.6 mm) analytical column (VWR, Darmstadt, Germany) protected by a Security Guard C18 (4×3 mm) guard column (Phenomex, Torrance, CA, USA) and with absorbance (345 nm) measured by a SPD-10ADVP UV detector (Shimadzu, Kyoto, Japan) The mobile phase consisted of an acetonitrile-phosphate buffer pH 2.5 (9:91, v/v) at a flow rate of 4.0 ml/min The calibration curve was linear or described by a power function from 40 to 2,840 nM (coefficient of determination >0.999) Where the ratio between the area of the sample and the area of the internal standard exceeded 0.3 and the linear concentration was greater than the power function concentration the linear concentration was used, otherwise the values derived from the power equation were used Quality control samples were included at three concentration levels (low, medium and high) and were run in duplicates The lower limit of quantification was nM and the within-day coefficient of variation was