Analysis of filter-paper-absorbed, finger-stick blood samples for chloroquine and its major metabolite using high-performance liquid chromatography with fluorescence detection

Determination of antimalarial drugs in pharmaceutical formulations and human blood by liquid chromatography: a review

Malaria is a life-threatening disease being treated by oral medication. This is the best treatment to reduce morbidity and mortality, prevent disease progression to the most severe form, lower the transmission of the disease and hinder the appearance of strains resistant to antimalarials. According to the World Health Organization, the most common antimalarial drugs are chloroquine, primaquine, mefloquine, lumefantrine, artemether, and artesunate in single dosage forms or fixed-dose combination. Within this context, the present review aims to show the evolution of different analytical methods that have been applied to the determination of these antimalarial drugs in pharmaceutical formulations and human blood by liquid chromatography in the last 10 years, along with statistical analyses of the methods.

HPLC methods for choloroquine determination in biological samples and pharmaceutical products

OBJECTIVE

Review and assess pharmaceutical and clinical characteristics of chloroquine including high-performance liquid chromatography (HPLC)-based methods used to quantify the drug in pharmaceutical products and biological samples.

EVIDENCE ACQUISITION

A literature review was undertaken on the PubMed, Science Direct, and Scielo databases using the following keywords related to the investigated subject: 'chloroquine', 'analytical methods', and 'HPLC'.

RESULTS

For more than seven decades, chloroquine has been used to treat malaria and some autoimmune diseases, such as lupus erythematosus and rheumatoid arthritis. There is growing interest in chloroquine as a therapeutic alternative in the treatment of HIV, Q fever, Whipple's disease, fungal, Zika, Chikungunya infections, Sjogren's syndrome, porphyria, chronic ulcerative stomatitis, polymorphic light eruption, and different types of cancer. HPLC coupled to UV detectors is the most employed method to quantify chloroquine in pharmaceutical products and biological samples. The main chromatographic conditions used to identify and quantify chloroquine from tablets and injections, degradation products, and metabolites are presented and discussed.

CONCLUSION

Research findings reported in this article may facilitate the repositioning, quality control, and biological monitoring of chloroquine in modern pharmaceutical dosage forms and treatments.

An Ultra-Sensitive Technique: Using Pv-mtCOX1 qPCR to Detect Early Recurrences of Plasmodium vivax in Patients in the Brazilian Amazon

BACKGROUND

Early recurrence of Plasmodium vivax is a challenge for malaria control in the field, particularly because this species is associated with lower parasitemia, which hinders diagnosis and monitoring through blood smear testing. Early recurrences, defined as the persistence of parasites in the peripheral blood despite adequate drug dosages, may arise from resistance to chloroquine. The objective of the study was to estimate early recurrence of P. vivax in the Brazilian Amazon by using a highly-sensitive detection method, in this case, PCR.

METHODS

An ultra-sensitive qPCR that targeted mitochondrial DNA was used to compare a standard qPCR that targeted 18S rDNA to detect early recurrence of P. vivax in very low densities in samples from patients treated with chloroquine.

RESULTS

Out of a total of 312 cases, 29 samples (9.3%) were characterized as recurrences, from which 3.2% (10/312) were only detected through ultra-sensitive qPCR testing.

CONCLUSIONS

Studies that report the detection of P. vivax early recurrences using light microscopy may severely underestimate their true incidence.

Analytical Methods on Determination in Pharmaceuticals and Biological Materials of Chloroquine as Available for the Treatment of COVID-19

With the outbreak caused by the severe acute respiratory syndrome coronavirus (COVID-19), people's health and existing economies on a global scale are seriously threatened. Currently, most of the countries all over the world are studying extensively to better understand the antimalarial chloroquine (CQ) and hydroxychloroquine (HCQ) for therapeutic purposes due to the COVID-19 outbreak. However, CQ and HCQ can have serious side effects, from psychiatric effects to sudden death. Therefore, a faster and more effective detection method is needed to monitor drug concentrations. In this review, a large study was conducted on the detection techniques and quantitative determination methods of CQ and its related metabolites. In this review, chromatography, electrophoresis, electroanalytical, spectroscopic, and immunological methods for CQ and related metabolites are discussed extensively. It is hoped that a better understanding of the CQ used for therapeutic purposes in the COVID-19 outbreak will be provided.

Chemoprophylaxis Vaccination: Phase I Study to Explore Stage-specific Immunity to Plasmodium falciparum in US Adults

BACKGROUND

Chemoprophylaxis vaccination with sporozoites (CVac) with chloroquine induces protection against a homologous Plasmodium falciparum sporozoite (PfSPZ) challenge, but whether blood-stage parasite exposure is required for protection remains unclear. Chloroquine suppresses and clears blood-stage parasitemia, while other antimalarial drugs, such as primaquine, act against liver-stage parasites. Here, we evaluated CVac regimens using primaquine and/or chloroquine as the partner drug to discern whether blood-stage parasite exposure impacts protection against homologous controlled human malaria infection.

METHODS

In a Phase I, randomized, partial double-blind, placebo-controlled study of 36 malaria-naive adults, all CVac subjects received chloroquine prophylaxis and bites from 12-15 P. falciparum-infected mosquitoes (CVac-chloroquine arm) at 3 monthly iterations, and some received postexposure primaquine (CVac-primaquine/chloroquine arm). Drug control subjects received primaquine, chloroquine, and uninfected mosquito bites. After a chloroquine washout, subjects, including treatment-naive infectivity controls, underwent homologous, PfSPZ controlled human malaria infection and were monitored for parasitemia for 21 days.

RESULTS

No serious adverse events occurred. During CVac, all but 1 subject in the study remained blood-smear negative, while only 1 subject (primaquine/chloroquine arm) remained polymerase chain reaction-negative. Upon challenge, compared to infectivity controls, 3/3 chloroquine arm subjects displayed delayed patent parasitemia (P = .01) but not sterile protection, while 3/11 primaquine/chloroquine subjects remained blood-smear negative.

CONCLUSIONS

CVac-primaquine/chloroquine is safe and induces sterile immunity to P. falciparum in some recipients, but a single 45 mg dose of primaquine postexposure does not completely prevent blood-stage parasitemia. Unlike previous studies, CVac-chloroquine did not produce sterile immunity.

CLINICAL TRIALS REGISTRATION

NCT01500980.

High sensitivity methods to quantify chloroquine and its metabolite in human blood samples using LC-MS/MS

Aim:

Chloroquine is an antimalarial drug used in the treatment of Plasmodium vivax malaria. Three methods to quantify chloroquine and its metabolite in blood matrices were developed and validated.

Methodology & results:

Different high-throughput extraction techniques were used to recover the drugs from whole blood (50 μl), plasma (100 μl) and dried blood spots (15 μl as punched discs) followed by quantification with LC–MS/MS. The intra- and inter-batch precisions were below 15%, and thus meet regulatory acceptance criteria.

Conclusion:

The developed methods demonstrated satisfactory validation performance with high sensitivity and selectivity. The assays used simple and easy to automate extraction techniques. All methods were reliable with robust performance and demonstrated to be suitable to implement into high-throughput routine analysis of clinical pharmacokinetic samples.

Comparison of artemether-lumefantrine and chloroquine with and without primaquine for the treatment of Plasmodium vivax infection in Ethiopia: A randomized controlled trial

BACKGROUND

Recent efforts in malaria control have resulted in great gains in reducing the burden of Plasmodium falciparum, but P. vivax has been more refractory. Its ability to form dormant liver stages confounds control and elimination efforts. To compare the efficacy and safety of primaquine regimens for radical cure, we undertook a randomized controlled trial in Ethiopia.

METHODS AND FINDINGS

Patients with normal glucose-6-phosphate dehydrogenase status with symptomatic P. vivax mono-infection were enrolled and randomly assigned to receive either chloroquine (CQ) or artemether-lumefantrine (AL), alone or in combination with 14 d of semi-supervised primaquine (PQ) (3.5 mg/kg total). A total of 398 patients (n = 104 in the CQ arm, n = 100 in the AL arm, n = 102 in the CQ+PQ arm, and n = 92 in the AL+PQ arm) were followed for 1 y, and recurrent episodes were treated with the same treatment allocated at enrolment. The primary endpoints were the risk of P. vivax recurrence at day 28 and at day 42. The risk of recurrent P. vivax infection at day 28 was 4.0% (95% CI 1.5%-10.4%) after CQ treatment and 0% (95% CI 0%-4.0%) after CQ+PQ. The corresponding risks were 12.0% (95% CI 6.8%-20.6%) following AL alone and 2.3% (95% CI 0.6%-9.0%) following AL+PQ. On day 42, the risk was 18.7% (95% CI 12.2%-28.0%) after CQ, 1.2% (95% CI 0.2%-8.0%) after CQ+PQ, 29.9% (95% CI 21.6%-40.5%) after AL, and 5.9% (95% CI 2.4%-13.5%) after AL+PQ (overall p < 0.001). In those not prescribed PQ, the risk of recurrence by day 42 appeared greater following AL treatment than CQ treatment (HR = 1.8 [95% CI 1.0-3.2]; p = 0.059). At the end of follow-up, the incidence rate of P. vivax was 2.2 episodes/person-year for patients treated with CQ compared to 0.4 for patients treated with CQ+PQ (rate ratio: 5.1 [95% CI 2.9-9.1]; p < 0.001) and 2.3 episodes/person-year for AL compared to 0.5 for AL+PQ (rate ratio: 6.4 [95% CI 3.6-11.3]; p < 0.001). There was no difference in the occurrence of adverse events between treatment arms. The main limitations of the study were the early termination of the trial and the omission of haemoglobin measurement after day 42, resulting in an inability to estimate the cumulative risk of anaemia.

CONCLUSIONS

Despite evidence of CQ-resistant P. vivax, the risk of recurrence in this study was greater following treatment with AL unless it was combined with a supervised course of PQ. PQ combined with either CQ or AL was well tolerated and reduced recurrence of vivax malaria by 5-fold at 1 y.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01680406.

Quantification of Warfarin in Dried Rat Plasma Spots by High-Performance Liquid Chromatography with Tandem Mass Spectrometry

This paper presents the development and validation of a novel method for quantification of the oral anticoagulant drug warfarin in dried plasma spots (DPS) by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Blood plasma was chosen as a biological fluid to preclude the influence of the hematocrit on the results of the analysis. A 30 μL sample of rat plasma was placed onto Whatman 903 Protein Saver Card and was allowed to dry. A single DPS is sufficient for preparing eight 3.2 mm discs, each containing approximately 1.5-1.6 μL of plasma. Warfarin extraction from one 3.2 mm disc was carried out by adding 200 μL of the acetonitrile : water mixture (1 : 1, v/v) containing 10 mM NH₄COOH (pH 4.0), with incubation on a shaker at 1000 rpm for 1 h at 25°C. After chromatographic separation, warfarin and coumachlor (an internal standard) were measured using negative-ion multiple-reaction monitoring with ion transitions m/z 307 → 161 for warfarin and m/z 341 → 161 for the internal standard. The working range of this method is 10-10,000 ng/mL. Within this range, intra- and interday variability of precision and accuracy was <13% and recovery was 82-99%. The results indicate that the new method requires only small plasma samples and may be useful for pharmacokinetic research on warfarin.

A DBS method for quantitation of the new oral trypanocidal drug fexinidazole and its active metabolites

AIM

Fexinidazole (FEX) is a nitroimidazole being developed as a new trypanocide treatment for human African trypanosomiasis/sleeping sickness. Its main metabolites, fexinidazole sulfoxide (M1) and fexinidazole sulfone (M2), show the same in vitro pharmacological activity as FEX.

METHODS & RESULTS

An LC-MS/MS assay was developed for quantitation of FEX in DBS, collected via finger-prick from healthy subjects. The DBS assay was specific, accurate and reproducible for FEX, M1 and M2 when validated against the current plasma assay. DBS samples were stable for 24 h at 37°C with 95% relative humidity, and 58 weeks desiccated at room temperature.

CONCLUSION

DBS finger-prick sampling offers a simple, practical method for determining FEX, M1 and M2 concentrations in clinical studies in Africa.

Efficacy in the treatment of malaria by Plasmodium vivax in Oiapoque, Brazil, on the border with French Guiana: the importance of control over external factors

Background

Plasmodium vivax malaria is an important public health issue in the Amazon region, and it accounts for approximately 84 % of cases of the disease. Migration across the border between Brazil and French Guiana contributes to the maintenance of the disease. The aim of this study was to evaluate the therapeutic and parasitological responses of patients with P. vivax malaria treated with chloroquine and primaquine in the socio-environmental context of cross-border interactions between Brazil and French Guiana. The factors controlled were diagnostic agreement, adherence, adjustment of primaquine doses for patient weight, and quality of the drugs used.

Methods

A prospective study was conducted in 2011 with 103 individuals aged 10–60 years with a positive diagnosis of P. vivax treated with chloroquine (10 mg base/kg on the first day, followed by 7.5 mg/kg on the second and third days) and primaquine for 7 days, who were followed for 28 days. The primaquine doses were adjusted for the patients’ weight. A number of factors were determined: epidemiological characteristics, origin of patients, signs and symptoms, initial parasitaemia and parasitaemia clearance time, blood concentrations of chloroquine and primaquine, quality of anti-malarial drugs and diagnostic agreement.

Results

Ninety-five patients were followed for 28 days. There was a 100 % agreement in microscopic diagnosis between field laboratory and reference centre. The adhesion to the treatment was 100 %. Of these patients, 32.6 % received a weight-adjusted dose of primaquine. The chloroquine and primaquine tablets were consistent with the optimal quality limits for human consumption. The investigated patients achieved optimal blood exposure to anti-malarial drugs. The parasitological and therapeutic response was adequate in 99.0 % of cases.

Conclusions

In the municipality of Oiapoque, the therapeutic regime used for the treatment of P. vivax malaria using chloroquine combined with primaquine remains effective, when external factors are controlled, such as the quality of anti-malarial drugs, the adhesion to the treatment prescribed, the correct diagnostic and the adjustment of primaquine dose for patient body weight.

Optimizing Intradermal Administration of Cryopreserved Plasmodium falciparum Sporozoites in Controlled Human Malaria Infection

Controlled human malaria infection (CHMI) is a powerful tool to evaluate malaria vaccine and prophylactic drug efficacy. Until recently CHMI was only carried out by the bite of infected mosquitoes. A parenteral method of CHMI would standardize Plasmodium falciparum sporozoite (PfSPZ) administration, eliminate the need for expensive challenge facility infrastructure, and allow for use of many P. falciparum strains. Recently, intradermal (ID) injection of aseptic, purified, cryopreserved PfSPZ was shown to induce P. falciparum malaria; however, 100% infection rates were not achieved by ID injection. To optimize ID PfSPZ dosing so as to achieve 100% infection, 30 adults aged 18-45 years were randomized to one of six groups composed of five volunteers each. The parameters of dose (1 × 10(4) versus 5 × 10(4) PfSPZ total dose per volunteer), number of injections (two versus eight), and aliquot volume per ID injection (10 μL versus 50 μL) were studied. Three groups attained 100% infection: 1 × 10(4) PfSPZ in 50 μL/2 doses, 1 × 10(4) PfSPZ in 10 μL/2 doses, and 5 × 10(4) PfSPZ in 10 μL/8 doses. The group that received 5 × 10(4) PfSPZ total dose in eight 10 μL injections had a 100% infection rate and the shortest prepatent period (mean of 12.7 days), approaching the prepatent period for the current CHMI standard of five infected mosquitoes.

Validation of a method for the simultaneous quantification of chloroquine, desethylchloroquine and primaquine in plasma by HPLC-DAD

One of the most important aspects regarding the therapeutic efficacy of antimalarials is its quantification in biologic fluids. The detection and measurement of antimalarial drug levels is important for demonstrating (1) adequate absorption of the drug being given, (2) compliance in taking the full regimen required for treatment and (3) the level of drug in the blood at any time during the test period that parasites reappear. There is a lack of validated methods that simultaneously quantify different antimalarials administered at the same time, such as the use of chloroquine (CQ) and primaquine (PQ) in infections caused by Plasmodium vivax. In this study, a bioanalytical method was validated for the simultaneous quantification of primaquine (PQ), chloroquine (CQ) and desethylchloroquine (DSCQ) in human plasma using liquid-liquid extraction and high performance liquid chromatography with a diode array detector (HPLC-DAD). The PQ was evaluated over a concentration range of 100-3000 nM and the CQ and DSCQ was evaluated over a concentration range of 20-2000 nM. The selectivity of the method was verified by checking for interference by commonly used antimalarials and plasma samples. The accuracy and precision of the method was assessed for drugs spiked into human plasma and recoveries of 83.7%, 92.3%, and 76.5% were obtained for CQ, DSCQ, and PQ, respectively. The applicability of this method was also demonstrated with blood samples from patients with vivax malaria that received combination CQ plus PQ treatment. The simultaneous detection and accurate measurement of CQ, DSCQ, and PQ levels in human plasma provides an important and economical method for validating and monitoring sensitivity/resistance of P. vivax to more common treatment regimen.

Plasmodium vivax chloroquine resistance and anemia in the western Brazilian Amazon

Data on chloroquine (CQ)-resistant Plasmodium vivax in Latin America is limited, even with the current research efforts to sustain an efficient malaria control program in all these countries where P. vivax is endemic and where malaria still is a major public health issue. This study estimated in vivo CQ resistance in patients with uncomplicated P. vivax malaria, with use of CQ and primaquine simultaneously, in the Brazilian Amazon. Of a total of 135 enrolled subjects who accomplished the 28-day follow-up, parasitological failure was observed in 7 (5.2%) patients, in whom plasma CQ and desethylchloroquine (DCQ) concentrations were above 100 ng/dl. Univariate analysis showed that previous exposure to malaria and a higher initial mean parasitemia were associated with resistance but not with age or gender. In the multivariate analysis, only high initial parasitemia remained significant. Hemoglobin levels were similar at the beginning of the follow-up and were not associated with parasitemia. However, at day 3 and day 7, hemoglobin levels were significantly lower in patients presenting CQ resistance. The P. vivax dhfr (pvdhfr), pvmrp1, pvmdr1, and pvdhps gene mutations were not related to resistance in this small sample. P. vivax CQ resistance is already a problem in the Brazilian Amazon, which could be to some extent associated with the simultaneous report of anemia triggered by this parasite, a common complication of the disease in most of the areas of endemicity.

Dried blood spots in bioanalysis of antimalarials: relevance and challenges in quantitative assessment of antimalarial drugs

Malaria is the leading parasitic disease in emerging countries. Therapeutic drug monitoring of antimalarial drugs is becoming increasingly important due to their spreading resistance. Measuring systemic antimalarial drug concentrations is also vital for safety and PK evaluations during clinical development. The dried blood spot (DBS) technique is a convenient alternative sample-collection method to venipuncture, especially in resource -limited areas where the clinical studies of antimalarials are usually carried out. Various bioanalytical methods for antimalarial drug estimation utilizing DBS sampling have been reported. This review discusses the applicability and relevance of DBS in quantitative assessment of antimalarial drugs, the advantages and drawbacks of DBS, and the difficulties encountered during its implementation.

Evaluation of the efficacy of chloroquine chemoprophylaxis for vivax malaria among Republic of Korea military personnel

Chloroquine has been used massively for vivax malaria prophylaxis and treatment in the Republic of Korea (ROK) military personnel from 1997. Although prophylaxis is generally regarded as successful among ROK military, prophylaxis failure has been repeatedly reported. Before the prophylaxis program was started on July 4th 2011, which was completed on October 16th 2011, by the ROK military, more than 60% of malaria cases were attributed to new infection or long-latency relapse. During the prophylaxis program, the authors re-examined the efficiency of chloroquine chemoprophylaxis in ROK military during the last 6 months of 2011 by measuring compliance and whole blood chloroquine levels in 41 malaria patients immediately before instituting antimalarial therapy between July and December. Three patients (7.3%) showed good compliance, and had whole blood total chloroquine levels above the minimally inhibitory concentration (100 ng/mL). However, 28 (69.3%) of these 41 patients when admitted to hospital showed poor or no compliance with prophylaxis; 4 of the 28 (14.3%) were stationed outside the mass prophylaxis region, and 5 (17.9%) subjects were infected after the prophylaxis program had finished. These findings indicate that the current malaria control program should be carefully reconsidered, in terms of, individual instruction, current chemoprophylaxis program regimens, and schedules to improve the efficacy of prophylaxis in the ROK military.

In vivo efficacy of artemether-lumefantrine and chloroquine against Plasmodium vivax: a randomized open label trial in central Ethiopia

BACKGROUND

In vivo efficacy assessments of antimalarials are essential for ensuring effective case management. In Ethiopia, chloroquine (CQ) without primaquine is the first-line treatment for Plasmodium vivax in malarious areas, but artemether-lumefantrine (AL) is also commonly used.

METHODS AND FINDINGS

In 2009, we conducted a 42-day efficacy study of AL or CQ for P. vivax in Oromia Regional State, Ethiopia. Individuals with P. vivax monoinfection were enrolled. Primary endpoint was day 28 cure rate. In patients with recurrent parasitemia, drug level and genotyping using microsatellite markers were assessed. Using survival analysis, uncorrected patient cure rates at day 28 were 75.7% (95% confidence interval (CI) 66.8-82.5) for AL and 90.8% (95% CI 83.6-94.9) for CQ. During the 42 days of follow-up, 41.6% (47/113) of patients in the AL arm and 31.8% (34/107) in the CQ arm presented with recurrent P. vivax infection, with the median number of days to recurrence of 28 compared to 35 days in the AL and CQ arm, respectively. Using microsatellite markers to reclassify recurrent parasitemias with a different genotype as non-treatment failures, day 28 cure rates were genotype adjusted to 91.1% (95% CI 84.1-95.1) for AL and to 97.2% (91.6-99.1) for CQ. Three patients (2.8%) with recurrent parasitemia by day 28 in the CQ arm were noted to have drug levels above 100 ng/ml.

CONCLUSIONS

In the short term, both AL and CQ were effective and well-tolerated for P. vivax malaria, but high rates of recurrent parasitemia were noted with both drugs. CQ provided longer post-treatment prophylaxis than AL, resulting in delayed recurrence of parasitemia. Although the current policy of species-specific treatment can be maintained for Ethiopia, the co-administration of primaquine for treatment of P. vivax malaria needs to be urgently considered to prevent relapse infections.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01052584.

Use of dried plasma spots for the quantification of iothalamate in clinical studies

BACKGROUND AND OBJECTIVES

Although iothalamate clearances have been widely used to measure GFR, the need for transportation of plasma samples under refrigerated conditions obviates its use in resource-poor situations. Spots of blood or plasma dried on filter paper may provide a solution.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using a validated HPLC technique, iothalamate in dried blood spots of different hematocrits was measured. GFR was measured over 5 hours in 10 subjects with CKD using dried plasma spots and standard methods.

RESULTS

Lower hematocrit produced greater area of blood spreading and lowered the recovery of iothalamate from dried blood spots. However, the relationship between iothalamate concentrations in dried plasma spots and plasma showed a regression slope of 0.95 (95% confidence interval=0.92-0.98, P<0.001). Bland-Altman plot of paired sample points (n=116) showed a bias of -4 μg/ml and limits of agreement of -38 to +30 μg/ml. The relationship between GFRs using dried plasma spots and plasma methods also showed an excellent relationship (slope of 0.95, 95% confidence interval=0.82-1.17). Bland-Altman plot of paired GFRs showed a bias of 2 ml/min, with limits of agreement of -6 to +10 ml/min. Precision was generally between 5% and 10%, and accuracy was within 5%.

CONCLUSIONS

Although dried blood spots are unsuitable for studies among those patients with very low hematocrit, dried plasma spots correct for this limitation, and this small pilot study shows that it is a reasonably reliable method for quantifying iothalamate and subsequently, determining GFR.

Phenotyping clinical resistance to chloroquine in Plasmodium vivax in northeastern Papua, Indonesia

Chloroquine (CQ)-resistant Plasmodium vivax was first documented in 1989 and threatens much of eastern Indonesia, with > 50% of therapeutic failure rates. We screened 2236 subjects for malaria infection through active case detection and identified 232 infected cases with 100 subjects carried P. vivax mono infection. We prospectively evaluated therapeutic responses to CQ in 73 subjects infected by P. vivax in northeastern Papua, Indonesia. We phenotyped these infections as susceptible or resistant to CQ using a 28-day in vivo test format. Eighteen subjects (25%) had persistent or recurrent parasitemia during the test and were provisionally classified as resistant. Among the remainder, 46 (63%) subjects had no persistent or recurrent parasitemia and were classified as having infections sensitive to CQ, 4 were lost to follow up, and 5 dropped out. Among the 18 provisionally resistant cases, 1 subject (6%) had persistent parasitemia at Day 3 and was considered as a direct treatment failure, 2 subjects (11%) had recurrent parasitemia by Day 7 and were considered early treatment failures, and 7 (39%) and 8 (44%) had recurrent parasitemia by Days 14 and 28, respectively. Analysis of blood for CQ+N-desethylchloroquine (DCQ) levels on day of recurrence from 15 of the 18 with treatment failures showed 11 subjects having CQ+DCQ blood levels ⩾ 100 ng/ml and 2 with CQ+DCQ blood levels < 100 ng/ml. The 28-day cumulative incidence of therapeutic failure likely due to parasite resistance was 17.5%. These findings affirm P. vivax resistance to CQ in eastern Indonesia, albeit at lower levels than reported elsewhere. This simple means of phenotyping P. vivax infections could be implemented in other malaria endemic areas of Indonesia.

Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection

BACKGROUND

More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.

RESULTS

This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-µl dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.

CONCLUSION

Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Evaluation of chloroquine therapy for vivax and falciparum malaria in southern Sumatra, western Indonesia

Background

Chloroquine was used as first-line treatment for Plasmodium falciparum or Plasmodium vivax in Indonesia before the initial launch of artemisinin combination therapy in 2004. A study to evaluate efficacies of chloroquine against P. falciparum and P. vivax was undertaken at Lampung in southern Sumatra, western Indonesia in 2002.

Methods

Patients infected by P. falciparum or P. vivax were treated with 25 mg/kg chloroquine base in three daily doses over 48 hr. Finger prick blood was collected on Days 0, 2, 3, 7, 14, 21 and 28 after starting drug administration. Whole blood chloroquine and its desethyl metabolite were measured on Days-0, -3 and -28, or on the day of recurrent parasitaemia.

Results

42 patients infected by P. falciparum were enrolled, and 38 fullfilled criteria for per protocol analysis. Only six of 38 (16%) showed a response consistent with senstivity to chloroquine. 25 of 32 failures were confirmed resistant by demonstrating chloroquine levels on day of recurrence exceeding the minimally effective concentration (200 ng/mL whole blood). The 28-day cumulative incidence of resistance in P. falciparum was 68% (95% CI: 0.5260 - 0.8306). Thirty one patients infected by P. vivax were enrolled, and 23 were evaluable for per protocol analysis. 15 out of 23 (65%) subjects had persistent or recurrent parasitaemia. Measurement of chloroquine levels confirmed all treatment failures prior to Day-15 as resistant. Beyond Day-15, 4 of 7 recurrences also had drug levels above 100 ng/mL and were classified as resistant. The 28-day cumulative incidence of chloroquine resistance in P. vivax was 43% (95% CI: 0.2715 - 0.6384).

Conclusion

These findings confirm persistantly high levels of resistance to chloroquine by P. falciparum in southern Sumatra, and suggest that high-grade and frequent resistance to chloroquine by P. vivax may be spreading westward in the Indonesia archipelago.

Dried-blood sampling for epstein-barr virus immunoglobulin G (IgG) and IgA serology in nasopharyngeal carcinoma screening

Dried-blood (DB) samples on filter paper are considered clinical specimens for diagnostic use because of the ease of collection, storage, and transport. We recently developed a synthetic-peptide-based immunoglobulin A (IgA) (EBNA1 plus viral capsid antigen [VCA]-p18) enzyme-linked immunosorbent assay (ELISA) for nasopharyngeal carcinoma (NPC) screening. Here, we evaluate the use of two filter papers for DB sampling, i.e., Schleicher & Schuell (S&S) no. 903 and Whatman no. 3; the DB samples were either taken directly from a finger prick or spotted from a Vacutainer blood collector. The elution of DB samples on filter paper was optimized and tested for IgG and IgA reactivity by ELISA (EBNA1 plus VCA-p18) and compared to simultaneously collected plasma samples. The results showed that both types of filter paper can be used for sample collection in NPC diagnosis by using either finger prick or blood spot sampling. Both DB sampling methods produced comparable ELISA (EBNA1 plus VCA-p18) results for IgG and IgA reactivity in 1:100-diluted plasma samples. DB samples of whole blood or finger prick blood show correlation coefficients (r(2)) of 0.825 to 0.954 for IgA on S&S no. 903 filter paper, 0.9133 to 0.946 for IgA on Whatman no. 3 filter paper, 0.807 to 0.886 for IgG on S&S no. 903 filter paper, and 0.819 to 0.934 for IgG on Whatman no. 3 filter paper. Using plasma IgA as a reference, DB sampling showed sensitivities and specificities of 75.0 to 96.0% and 93.5 to 100%, respectively. DB samples could be stored at 37 degrees C for 1 to 4 weeks on S&S no. 903 filter paper and 1 to 6 weeks on Whatman no. 3 filter paper without a significant loss of reactivity, with provision of transport options for tropical conditions. IgA proved to be more stable than IgG. Whatman no. 3 filter paper is a more economical yet diagnostically comparable alternative to S&S no. 903 filter paper. Finger prick DB sampling is proposed for NPC diagnosis, particularly for remote hospitals and field screening studies.

Practical HPLC methods for the quantitative determination of common antimalarials in Africa

This article describes high-performance liquid chromatographic assays for the quantification of sulfadoxine (SDX), pyrimethamine (PYM), chloroquine (CQ), amodiaquine (AQ) and desethylamodiaquine (AQM) from whole blood. All four assays were set up and validated in Malawi using a common high-performance liquid chromatography platform and column and involved the use of simple mobile phase and extraction reagents. Calibration curves were linear (r(2)>0.95) in the ranges 5-100microg/ml, 50-1000, 150-1500, 100-1000 and 100-1000ng/ml for SDX, PYM, CQ, AQ and AQM, respectively. Intra-assay and inter-assay coefficients of variation were <15% at 3 points spanning the concentration range and <20% at the lower limit of quantification. The assays were specific with no interference from the other antimalarials described in this report. All four assays use liquid-liquid extraction, reversed-phase chromatography and UV detection and require between 50 and 200microl of blood. Because the assays share common instruments and reagents, they are cost-efficient and could be used to optimise antimalarial drug therapies in other resource poor settings.

The drug sensitivity and transmission dynamics of human malaria on Nias Island, North Sumatra, Indonesia

Nias Island, off the north-western coast of Sumatra, Indonesia, was one of the first locations in which chloroquine-resistant Plasmodium vivax malaria was reported. This resistance is of particular concern because its ancient megalithic culture and the outstanding surfing conditions make the island a popular tourist destination. International travel to and from the island could rapidly spread chloroquine-resistant strains of P. vivax across the planet. The threat posed by such strains, locally and internationally, has led to the routine and periodic re-assessment of the efficacy of antimalarial drugs and transmission potential on the island. Active case detection identified malaria in 124 (17%) of 710 local residents whereas passive case detection, at the central health clinic, confirmed malaria in 77 (44%) of 173 cases of presumed 'clinical malaria'. Informed consenting volunteers who had malarial parasitaemias were treated, according to the Indonesian Ministry of Health's recommendations, with sulfadoxine-pyrimethamine (SP) on day 0 (for P. falciparum) or with chloroquine (CQ) on days 0, 1 and 2 (for P. vivax). Each volunteer was then monitored for clinical and parasite response until day 28. Recurrent parasitaemia by day 28 treatment was seen in 29 (83%) of the 35 P. falciparum cases given SP (14, 11 and four cases showing RI, RII and RIII resistance, respectively). Recurrent parasitaemia was also observed, between day 11 and day 21, in six (21%) of the 28 P. vivax cases given CQ. Although the results of quantitative analysis confirmed only low prevalences of CQ-resistant P. vivax malaria, the prevalence of SP resistance among the P. falciparum cases was among the highest seen in Indonesia. When the parasites present in the volunteers with P. falciparum infections were genotyped, mutations associated with pyrimethamine resistance were found at high frequency in the dhfr gene but there was no evidence of selection for sulfadoxine resistance in the dhps gene. Night-biting mosquitoes were surveyed by human landing collections and tested for sporozoite infection. Among the five species of human-biting anophelines collected, Anopheles sundaicus was dominant (68%) and the only species found to be infective--two (1.2%) of 167 females being found carrying P. vivax sporozoites. The risk of malarial infection for humans on Nias was considered high because of the abundance of asymptomatic carriers, the reduced effectiveness of the available antimalarial drugs, and the biting and infection 'rates' of the local An. sundaicus.

High-performance liquid chromatographic assay for the simultaneous determination of sulfadoxine and pyrimethamine from whole blood dried onto filter paper

A method using solid-phase extraction and high-performance liquid chromatography is evaluated for the simultaneous determination of sulfadoxine and pyrimethamine from 0.1 ml of whole blood dried onto filter paper. Extraction recoveries are about 60% for both drugs. The coefficient of variation for intra-assay precision, inter-assay precision and accuracy is less than 10% for sulfadoxine (10-100 microg/ml) and pyrimethamine (1-10 microg/ml).

Use of filter paper for the collection and analysis of human whole blood specimens

The Centers for Disease Control and Prevention and its partners have been operating the Newborn Screening Quality Assurance Program for >20 y. The program helps participating laboratories to evaluate and improve the quality of their newborn-screening testing efforts by providing quality control dried blood spot materials and proficiency-testing materials for the external evaluation of screening programs. The Newborn Screening Quality Assurance Program provides an independent evaluation of filter papers approved by the Food and Drug Administration for the collection of blood for clinical tests. These activities have created a mechanism for the validation of the filter paper blood collection device and the standardization of materials and methods for the analysis of dried blood spots.

Chloroquine is not a risk factor for seizures in childhood cerebral malaria

OBJECTIVES

There are a number of case reports in the medical literature suggesting an association between the ingestion of chloroquine and subsequent seizure activity. Our study was designed to investigate the relationship between blood levels of chloroquine (CQ), its metabolite desethylchloroquine (DCQ), and seizures in children admitted to hospital with cerebral malaria.

METHODS

Serial blood levels of CQ and DCQ were measured over the first 24 h of hospital admission in children with cerebral malaria. The number and duration of all seizures was recorded, and statistical analysis subsequently performed to determine the relationship between seizure activity and blood concentrations of CQ and DCQ.

RESULTS

Chloroquine was detected in 92% (100/109) of admission blood samples. 54% (59/109) of the patients had one or more seizures after admission, while 8% (9/109) had an episode of status epilepticus. Median (interquartile range) baseline concentrations of CQ and DCQ were, respectively, 169.4 microg/ml (75.1-374.9) and 352.3 microg/ml (81.9-580.1) for those children who had seizures after admission, compared to CQ 227.5 microg/ml (79.4-430.2) and DCQ 364.0 microg/ml (131.3-709.4) for those who did not have seizures (P > 0.5 for all comparisons). Baseline concentrations of CQ and DCQ were not significantly associated with the occurrence of seizures lasting for 5 min or more. The nine children who had an episode of status epilepticus had significantly lower median admission levels of CQ than those without status epilepticus: 75.1 microg/l (7.4-116.5) vs. 227.5 microg/l (85.6-441.2), P = 0.02. Multivariate logistic regression analysis, taking into account factors likely to affect the risk of seizures in hospital, failed to change the significance of these results.

CONCLUSIONS

These findings suggest that chloroquine does not play an important role in the aetiology of seizures in childhood cerebral malaria.

Fatal chloroquine intoxication

A suicidal ingestion of an unknown quantity of Resochin (chloroquine) tablets is described. Although chloroquine is known since 1934, intoxications due to chloroquine overdose are rather rare in European countries. The authors report on a new and fast method of analysing and determining the chloroquine concentration in body fluids and postmortem specimens. The analytes were extracted from alkalinized samples into ethyl acetate before GC/MS analysis. The analyses of chloroquine were performed without any complex sample clean-up steps and, in addition, with little sample material. The proposed method resulted in a rapid procedure most useful in cases of deliberate poisoning with the anti-inflammatory and antimalarial drug chloroquine.

Chlorproguanil-dapsone: effective treatment for uncomplicated falciparum malaria

Pyrimethamine-sulfadoxine, the first choice for uncomplicated falciparum malaria in Africa, exerts strong selection pressure for resistance because of its slow elimination. It is likely that resistance will emerge rapidly, and there is no widely affordable replacement. Chlorproguanil-dapsone is cheap, rapidly eliminated, more potent than pyrimethamine-sulfadoxine, and could be introduced in the near future to delay the onset of antifolate resistance and as "salvage therapy" for pyrimethamine-sulfadoxine failure. A total of 448 children were randomly allocated (double blind) to either a single dose of pyrimethamine-sulfadoxine or to one of two chlorproguanil-dapsone regimens: a single dose or three doses at 24-h intervals. Reinfections are clinically indistinguishable from recrudescence and are more likely after treatment with rapidly eliminated drugs; we measured the incidence of parasitemia in 205 initially aparasitemic children to allow comparison with the three treatment groups. The patients and a community surveillance group were followed up for 28 days. At the study end point, 31.2% (95% confidence interval, 24.9-38.0) of the community surveillance group subjects were parasitemic, compared with subjects in the treatment groups, whose rates of parasitemia were 40.8% (32.9-49.0; relative risk [RR], 1.31 [0.99-1.73]) after triple-dose chlorproguanil-dapsone, 19.7% (13.5-27.2; RR, 0.63 [0.43-0.93]) after pyrimethamine-sulfadoxine, and 65.6% (57.5-73.0; RR, 2.10 [1.66-2.65]) after single-dose chlorproguanil-dapsone. Pyrimethamine-sulfadoxine and triple-dose chlorproguanil-dapsone were effective treatments. Pyrimethamine-sulfadoxine provided chemoprophylaxis during follow-up because of its slow elimination. Triple-dose chlorproguanil-dapsone should now be developed in an attempt to reduce the rate of emergence of antifolate resistance in Africa and for affordable salvage therapy in cases of pyrimethamine-sulfadoxine failure.

Diagnosis of a case of acute chloroquine poisoning using 1H NMR spectroscopy: characterisation of drug metabolites in urine

Analysis of biological fluids by proton nuclear magnetic resonance spectroscopy (1H NMR) is a promising tool in clinical biology. We have used this method for a rapid toxicological screening in the case of a suicide attempt. A urine sample was analysed at 300 and 600 MHz by 1D and 2D sequences (J-resolved and TOCSY) in a short experimental time. Quantification was realized by peak integration of the 1D spectrum. The results showed the presence of chloroquine and its major metabolite monodesethylchloroquine at concentrations of 462 and 140 mg/L, respectively. Ethanol was also detected in the spectrum. It can be concluded that 1H NMR provides many advantages as a tool for clinical diagnosis in a case of acute intoxication.

Survey of resistance to chloroquine by Plasmodium vivax in Indonesia

In February 1995 we surveyed to chloroquine among patients with Plasmodium vivax malaria at Nias Island, in the Indian Ocean near north-western Sumatra, Indonesa. The subjects, 21 indigenous males and females (6-50 years old) infected with > 40 asexual blood stage parasites of P. vivax per microliter of blood, had mild symptoms or none at all. Seven of these patients had > 100 ng/mL whole blood chloroquine levels before the first supervised dose of chloroquine (3 doses of 10 mg/kg, 10 mg/kg, 5 mg/kg of base given at 24 h intervals). Whole blood chloroquine levels on the last day of dosing confirmed normal absorption (range 413-3248, mean 1141, SD 616 ng/mL). Blood films were examined on days 0, 2, 4, 7, 11, 14, 18, 21 and 28 after initiating therapy. Three patients had recurrent asexual P. vivax parasitaemias between days 14 and 18, despite effective levels of chloroquine in whole blood (> or = 100 ng/mL) at the time of recurrence. Resistance to standard chloroquine therapy by P. vivax appeared in 14% of infections among residents of Nias.

Plasmodium falciparum: increased proportion of severe resistance (RII and RIII) to chloroquine and high rate of resistance to sulfadoxine-pyrimethamine in Peninsular Malaysia after two decades

Uncomplicated falciparum malaria patients were randomly assigned to receive either 25 mg/kg chloroquine (CHL) over 3 d or a statim dose of 25 mg/kg sulfadoxine (SDX) plus 1.25 mg/kg pyrimethamine (PYR). Patients were followed up for 28 d and the parasite response graded according to World Health Organization criteria. Overall resistance to CHL was 63.3% and 47.4% to SDX/PYR. RI, RII and RIII rates were 9.1%, 42.4% and 12.1% for CHL and 10.5%, 21.1% and 15.8% for SDX/PYR, respectively. Degree and rates of resistance to CHL were significantly correlated with pre-treatment parasite density, but not those to SDX/PYR. Plasma CHL and SDX/PYR levels were within the reported ranges and were not significantly different in patients with sensitive and resistant responses.

Determination of proguanil and metabolites in small sample volumes of whole blood stored on filter paper by high-performance liquid chromatography

A method is reported for the determination of proguanil and its two metabolites cycloguanil and 4-chlorophenylbiguanide in whole blood and plasma samples obtained by thumbprick and stored dry on filter paper. The sample preparation involves liquid extraction from the filter paper and subsequent solid-phase extraction using C8 Bond-Elut cartridges. Separation and quantification is by a previously reported ion-pairing high-performance liquid chromatographic system with ODS Hypersil as stationary phase and an 50:50 acetonitrile-pH 2 phosphate buffer mobile phase containing 200 mM sodium dodecylsulphate as ion-pairing agent. The analytical characteristics of the method are reported. Representative concentrations are shown as a function of time from a human subject after ingestion of a single 200-mg dose of proguanil hydrochloride. Typical ranges of concentration detected by the proposed method in human subjects were proguanil 12-900 ng/ml, cycloguanil 16-44 ng/ml and 4-chlorophenylbiguanide 1.5-10 ng/ml in whole blood.

Laboratory methods for the conduct of experimental malaria challenge of volunteers

Experimental malaria challenge trials of volunteers are conducted to determine whether candidate sporozoite vaccines generate protective immunity against the bites of infected mosquitoes. The absence of patent erythrocytic-stage infection and clinical sequelae suggests sterile immunity among vaccinated volunteers. Sterile immunity is validated through laboratory studies that (1) demonstrate the capacity of erythrocytes and serum obtained from each volunteer before challenge to support parasite growth in vitro; (2) confirm parasitaemia by blood culture, and (3) evaluate each volunteer's blood for surreptitious use of antimalarial agents. The bites of experimentally infected laboratory-reared anophelines must elicit a 100% attack rate among non-immunized volunteers. This report presents guidelines for the laboratory methods used to validate the clinical findings during experimental Plasmodium falciparum anti-sporozoite vaccine efficacy trials.

High-performance liquid chromatographic method for the simultaneous determination of mefloquine and its carboxylic metabolite in 100-microliters capillary blood samples dried on paper

A reversed-phase high-performance liquid chromatographic method is described for the analysis of mefloquine and its carboxylic metabolite in 100-microliters capillary blood spots dried on chromatographic paper. Each spot was cut into small pieces, and mefloquine and its metabolite were eluted with an ammonia-water solution (10:90, v/v). The compounds were extracted simultaneously after alkalization at pH 9.5 using tetrabutylammonium as ion-pairing agent and then separated on a C18 column with ultraviolet detection at 227 nm. The recovery of the drugs from spiked blood applied to paper and dried was 70-80%, and the inter-assay precision at 1.0-5.0 mumol/l (therapeutic range) was less than 10%. The correlation between extractions from venous whole blood and capillary blood applied to chromatographic paper was more than 0.94. The analytes were stable in dried blood spots for at least fifty days at -20 degrees C. The decrease of concentration was less than 10%, when the paper was stored at 37 degrees C for fifty days. The assay is reliable and easy to use for therapeutic monitoring of mefloquine with a lower limit of determination of 0.3-0.5 mumol/l.

Simultaneous determination of chloroquine and quinine in human biological fluids by high-performance liquid chromatography

A high-performance liquid chromatographic method with fluorescence detection is described for the simultaneous measurement of quinine, chloroquine and mono- and bidesethylchloroquine in human plasma, erythrocytes and urine. After a liquid-solid extraction on a Bond Elut C8 cartridge, the compounds are separated on an Inertsil silica column by gradient elution; the mobile phase is a mixture of acetonitrile and methanol-25% ammonia solution (92.7:7.5, v/v). The eluent was monitored with a fluorescence detector (excitation wavelength 325 nm and emission wavelength 375 nm). The limit of detection was ca. 5 ng/ml for chloroquine and ca. 23 ng/ml for quinine. No chromatographic interferences could be detected from endogenous compounds or other antimalarial drugs. The method is accurate with inter- and intra-assay coefficients of variation lower than 7%. Hydroxychloroquine is used as an internal standard because of its structural similarity to chloroquine. The procedure requires 30 min and can be used for therapeutic drug monitoring.

Vivax malaria resistant to treatment and prophylaxis with chloroquine

Chloroquine has been the treatment of choice for vivax malaria for more than 40 years. Lately, several case-reports have suggested the emergence of resistance to chloroquine in Plasmodium vivax in Papua New Guinea and Indonesia. We undertook prospective treatment and prophylaxis trials of chloroquine in children and adults with vivax malaria living in Irian Jaya (Indonesia New Guinea). 46 villagers with P vivax parasitaemia were treated with chloroquine by mouth (25 mg base/kg body weight divided over 3 days) and followed up for 14 days. Parasitaemia cleared initially but recurred within 14 days in 10 (22%) subjects. All recurrences were in children younger than 11 years, 7 of whom were younger than 4 years; the failure rate among children under 4 was 70%. 7 of the patients with recurrences were given a second course of chloroquine. In all, the infections initially cleared but recurrent parasitaemia developed in 5 (71%) within 14 days. Whole-blood chloroquine concentrations were consistently above those previously shown to cure P vivax blood infections (90 micrograms/L whole blood). Subjects whose initial infections cleared and who had no parasitaemia on day 14 received weekly prophylaxis with chloroquine. Despite the presence of expected blood chloroquine concentrations, P vivax parasitaemia developed in 9 of 17 subjects receiving prophylaxis during 8 weeks of follow-up (median time to parasitaemia 5.3 weeks). Chloroquine can no longer be relied upon for effective treatment or chemoprophylaxis of P vivax blood infections acquired in this part of New Guinea.

Measurement of halofantrine and its major metabolite desbutylhalofantrine in plasma and blood by high-performance liquid chromatography: a new methodology

A new high-performance liquid chromatographic assay for the measurement of halofantrine and desbutylhalofantrine in plasma and whole blood is described. The method involves a smaller sample volume, simplified sample pre-treatment and a shorter run-time, and is adaptable to the measurement of samples dried onto filter paper strips. Using this method, which is both selective and sensitive, plasma concentration versus time profiles for both substances have been investigated following a single oral dose (500 mg) of halofantrine hydrochloride to a healthy adult volunteer. In addition, a clinical study designed to evaluate the disposition and elimination of the two compounds in children with non-severe falciparum malaria is in progress.

Measurement of quinine in filter paper-absorbed blood by high-performance liquid chromatography

An adaptation of an existing high-performance liquid chromatographic assay is described for the measurement of quinine, within the therapeutic concentration range, in whole blood. This method, in particular the use of small blood samples which have been dried onto filter paper strips, has advantages for clinical and pharmacokinetic studies in the tropics on children with malaria.