Incidence of antimalarial pretreatment and drug sensitivity in vitro in multidrug-resistant Plasmodium falciparum infection in Thailand

Compliance with a three-day course of artesunate-mefloquine combination and baseline anti-malarial treatment in an area of Thailand with highly multidrug resistant falciparum malaria

Background

Artemisinin-based combination therapy (ACT) is presently recommended by the World Health Organization as first-line treatment for uncomplicated Plasmodium falciparum malaria in several countries, as a mean of prolonging the effectiveness of first-line malaria treatment regimens. A three-day course of artesunate-mefloquine (4 mg/kg body weight once daily for three consecutive days, plus 15 and 10 mg/kg body weight mefloquine on the first and second days) has been adopted by Malaria Control Programme of Thailand as first-line treatment for uncomplicated falciparum malaria all over the country since 2008. The gametocytocydal anti-malarial drug primaquine is administered at the dose of 30 mg (0.6 mg/kg) on the last day. The aim of the present study was to assess patient compliance of this combination regimen when applied to field condition.

Methods

A total of 240 patients (196 males and 44 females) who were attending the malaria clinics in Mae-Sot, Tak Province and presenting with symptomatic acute uncomplicated falciparum malaria, with no reappearance of Plasmodium vivax parasitaemia during follow-up were included into the study. The first dose of the treatment was given to the patients under direct supervision. All patients were given the medication for self-treatment at home and were requested to come back for follow-up on day 3 of the initial treatment. Baseline (day 0) and day 3 whole blood mefloquine and plasma primaquine concentrations were determined by high performance liquid chromatography.

Results

Two patients had recrudescence on days 28 and 35. The Kaplan-Meier estimate of the 42-day efficacy rate of this combination regimen was 99.2% (238/240). Based on whole blood mefloquine and plasma primaquine concentrations on day 3 of the initial treatment, compliance with mefloquine and primaquine in this three-day artesunate-mefloquine combination regimen were 96.3% (207/215), and 98.5% (197/200), respectively. Baseline mefloquine and primaquine levels were observed in 24 and 16% of the patients.

Conclusion

The current first-line treatment and a three-day combination regimen of artesunate-mefloquine provides excellent patient compliance with good efficacy and tolerability in the treatment of highly multidrug resistance falciparum malaria. Previous treatment with mefloquine and primaquine were common in this area.

Drug-resistant Plasmodium falciparum infection in immigrants and non-immune travellers

OBJECTIVE

To detect the incidence of drug-resistant Plasmodium falciparum malaria infection in immigrants and travellers in non-endemic Kuwait.

METHODS

Over a period of 3 years, July 1995 to September 1998, 1352 malaria patients were enrolled in the study. Of these, 1293 were immigrants from countries where malaria is endemic and 59 were non-immune travellers with a recent history of travel to these countries. The in vitro drug sensitivity was determined in 892 patients.

RESULTS

In all, 892 of 1352 (66.0%) P. falciparum isolates were successfully cultured in vitro for drug sensitivity and 419 (47.0%) isolates showed in vitro resistance to chloroquine or mefloquine. Fifty-six (13.4%) isolates were resistant to both drugs. Chloroquine resistance was observed in > 70% of the isolates from Africa and India followed by Pakistan (39.9%) and Bangladesh (35.9%). The resistance to mefloquine ranged from 26.2% in isolates from Sri Lanka to 47.5% in isolates from African countries.

CONCLUSION

The study highlights the important trend in drug resistance in P. falciparum malaria in immigrants from south-east Asian and African countries.

Molecular characterisation of drug-resistant Plasmodium falciparum from Thailand

BACKGROUND

The increasing levels of Plasmodium falciparum resistance to chloroquine (CQ) in Thailand have led to the use of alternative antimalarials, which are at present also becoming ineffective. In this context, any strategies that help improve the surveillance of drug resistance, become crucial in overcoming the problem.

METHODS

In the present study, we have established the in vitro sensitivity to CQ, mefloquine (MF), quinine (QUIN) and amodiaquine (AMQ) of 52 P. falciparum isolates collected in Thailand, and assessed the prevalence of four putative genetic polymorphisms of drug resistance, pfcrt K76T, pfmdr1 N86Y, pfmdr1 D1042N and pfmdr1 Y1246D, by PCR-RFLP.

RESULTS

The percentage of isolates resistant to CQ, MF, and AMQ was 96% (50/52), 62% (32/52), and 58% (18/31), respectively, while all parasites were found to be sensitive to QUIN. In addition, 41 (79%) of the isolates assayed were resistant simultaneously to more than one drug; 25 to CQ and MF, 9 to CQ and AMQ, and 7 to all three drugs, CQ, MF and AMQ. There were two significant associations between drug sensitivity and presence of particular molecular markers, i) CQ resistance / pfcrt 76T (P = 0.001), and ii) MF resistance / pfmdr1 86N (P < 0.001)

CONCLUSIONS

i) In Thailand, the high levels of CQ pressure have led to strong selection of the pfcrt 76T polymorphism and ii) pfmdr1 86N appears to be a good predictor of in vitro MF resistance.

Absence of significant pharmacokinetic and pharmacodynamic interactions between artemether and quinoline antimalarials

The study was carried out to investigate the pharmacokinetic and pharmacodynamic interactions between artemether (ARTEM) and quinoline antimalarials namely mefloquine (MQ), quinine (QN) and primaquine (PQ) when given concurrently. A randomised comparative, seven way cross-over design was performed in eight healthy male Thais following the administrations of seven drug regimens on seven occasions i.e. a single oral dose of ARTEM (300 mg), or MQ (750 mg), or QN (600 mg), or PQ (45 mg) alone, or the combination of ARTEM (300 mg) with MQ (750 mg), or QN (600 mg), or PQ (45 mg). All clinical and laboratory parameters were normal in all subjects, before, during and after the study. The eight subject experienced no adverse effect after ARTEM, QN, PQ alone regimens, or combination of ARTEM with QN and PQ. After administration of MQ in either occasion, 3 subjects had weakness, nausea, abdominal pain, and diarrhoea; one subject complained of dizziness. All symptoms were mild and occurred during the first day of MQ administration. The fitting of the concentration-time curves of ARTEM, QN and PQ, to a one-compartment model with first order absorption yielded satisfactory results in all subjects. The best fit model for MQ was two-compartment model with first order absorption. The pharmacokinetics of all investigated drug, when given alone or in combination were not significantly different.