Validation and Pharmacokinetic Application of a High-Performance Liquid Chromatographic Technique for Determining the Concentrations of Amodiaquine and Its Metabolite in Plasma of Patients Treated with Oral Fixed-Dose Amodiaquine-Artesunate Combination in Areas of Malaria Endemicity

Abstract

dArtemisinin-based combination therapies (ACTs) have been adopted by most African countries, including Nigeria, as first-line treatments for uncomplicated falciparum malaria. Fixed-dose combinations of these ACTs, amodiaquine-artesunate (FDC AQAS) and artemether-lumefantrine (AL), were introduced in Nigeria to improve compliance and achieve positive outcomes of malaria treatment. In order to achieve clinical success with AQAS, we developed and validated a simple and sensitive high-performance liquid chromatography (HPLC) method with UV detection for determination of amodiaquine (AQ) and desethylamodiaquine (DAQ) in plasma using liquid-liquid extraction of the drugs with diethyl ether following protein precipitation with acetonitrile. Chromatographic separation was achieved using an Agilent Zorbax C 18 column and a mobile phase consisting of Extensive deployment of antimalarial drugs in the past 50 years has led to high selection pressure on human malaria parasites to evolve mechanisms of resistance. Plasmodium falciparum is now highly resistant to chloroquine (a one-time first-line antimalarial) and other antimalarials in most malaria-affected areas. Due to the relentless increase in resistance of malaria parasites to conventional drugs, many African countries have adopted the WHO recommendation to use artemisinin-based combination therapies (ACTs) as the first-line treatment for uncomplicated falciparum malaria (1). Artemisinin derivatives rapidly reduce the biomass of multidrug-resistant parasites, leaving the partner drugs, which usually have longer half-lives and therefore are eliminated more slowly, to kill the remaining residual parasites. The complete clearance of all parasites is therefore dependent on the partner drugs, such as amodiaquine (AQ), lumefantrine, piperaquine, and mefloquine, being effective and persisting at parasiticidal concentrations until all infecting parasites are killed. A fixed-dose combination (FDC) of AQ and artesunate (AS) tablets (Diasunate; Emzor, Lagos, Nigeria) was introduced to the Nigerian market to improve patient compliance and achieve a positive outcome of malaria treatment. Following oral administration of AQ, there is rapid and extensive metabolism of the AQ to its pharmacologically active derivative desethylamodiaquine (DAQ), which is assumed to be responsible for most of the therapeutic effect (2); in vitro studies (3-5), however, suggest synergism between AQ and DAQ (Fig. 1). This underscores the importance of routine therapeutic drug monitoring when artesunate is coadministered with AQ, to ensure not only appropriate drug dosing, but also that the dosing regimen results in concentrations in the blood sufficiently high to kill the residual parasites. A diseased state significantly alters the disposition of antimalarial drugs, yet several analytical techniques that reported the quantification of AQ and DAQ (2, 6-13) in various biological fluids demonstrated its applicability only either in healthy volunteers or in patients administered AQ as monotherapy. To our know...

Moringa oleifera leaf powder alters the pharmacokinetics of amodiaquine in healthy human volunteers

“…The plasma concentration‐time profiles of AQ and DEAQ in all the arms of this study are as shown in Figures and , respectively, whereas the derived pharmacokinetic parameters for AQ and DEAQ are as shown in Tables and , respectively. In this study, as it had been reported in previous human studies involving the administration of a single dose of AQ, there was rapid absorption and an extensive metabolism of AQ to its pharmacologically active derivative, DEAQ, which is thought to be responsible for most of the therapeutic effect of the drug . In fact, AQ was cleared from the system within 30 minutes and it has been rightly suggested that DEAQ should be monitored in vivo during malaria therapy instead of AQ.…”

“…Blood samples were collected before dosing and at 0.25, 0.5, 1, 2, 4, 8, 12 and 24 hours into heparinized tubes and immediately centrifuged at 4000 rpm (2147 g ) for 10 minutes to obtain plasma which were stored at −20°C until analysis. Plasma concentrations of amodiaquine (AQ) and desethylamodiaquine (DEAQ) were simultaneously determined using a modified validated HPLC method . For sample preparation, 10 μL of a 1 ng/mL hydroxychloroquine (HCQ) solution was added to 500 μL of plasma in an extraction tube and made up to 2 mL with distilled water and vortex‐mixed for 1 minute.…”

Induction of Amodiaquine Metabolism by Rifampicin Following Concurrent Administration in Healthy Volunteers

“…Plasma samples were analyzed for ADQ and DEAQ using the HPLC method reported by Adedeji et al 24 Sample extraction involved precipitation of the plasma proteins, followed by extraction as follows: in a 15 mL extraction tube, 1 mL of plasma, 1 mL of acetonitrile and 2 µL of 50 µg/mL of hydroxychloroquine (internal standard) were added and centrifuged for 20 min at 3,000 ×g to precipitate the plasma protein. The supernatant was then separated into clean and dry extraction tubes, to which 2 mL of diethyl ether was added.…”

“…The calibration procedures were as reported. 24 A calibration curve, based on peak area ratio, was prepared by spiking drug-free plasma with standard solutions of ADQ and DEAQ to give concentration ranges of 100-1,000 ng/mL for both ADQ and DEAQ. The samples were taken through the extraction procedure described above.…”

Research progress in electroanalytical techniques for determination of antimalarial drugs in pharmaceutical and biological samples

“…[4][5][6][7][8][9][10][11][12][13] However, last few decades witnessed an upsurge in electrochemical methods for the detection and determination of these compounds. Therapeutic drug monitoring (TDM) is a clinical strategy that measures drug concentration in a patient's bloodstream to monitor its compliance, efficacy and toxicity, thus optimizing and managing individual medication regimen.…”