Activity of artemether-azithromycin versus artemether-doxycycline in the treatment of multiple drug resistant falciparum malaria.

The efficacy of the combination of artemether with doxycycline or azithromycin was evaluated in 60 patients with acute uncomplicated falciparum malaria who attended malaria clinic in Mae Sot, Tak Province (Thai-Myanmar border). Patients (30 each) were randomized to receive (a) 300 mg artemether together with 100 mg doxycycline as initial doses, followed by 100 mg artemether plus 100 mg doxycycline at 12 hours later, then 100 mg doxycycline every 12 hours for another 4 days, or (b) 300 mg artemether together with 500 mg azithromycin, followed by 250 mg azithromycin at 24 and 48 hours. The follow-up period was 28 days. Patients in either group had a rapid initial response to treatment with comparable PCT and FCT. The cure rate of artemether-azithromycin regimen was significantly lower than that of artemether-doxycycline regimen (14.8 vs 53.3%). Low cure rate from artemether-azithromycin combination in this study was likely to be due to inadequate azithromycin dosage. However, with the low incidence of gastrointestinal adverse effects, the once daily dose of azithromycin could still be increased in order to enhance its clinical efficacy. The simplicity of drug administration and lesser incidence of adverse effects make azithromycin a more proper partner of artemether than doxycycline. Further dose-finding and pharmacokinetic study with the artemether-azithromycin combination is encouraging.

Artemether-pyrimethamine in the treatment of pyrimethamine-resistant falciparum malaria.

In vitro susceptibility and clinical response of multidrug resistant Plasmodium falciparum to the combination artemether-pyrimethamine were evaluated in patients with acute uncomplicated falciparum malaria. Sixty patients were randomized to receive 3 oral regimens of the combination artemether-pyrimethamine as follows: Regimen-I: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then placebo on the two consecutive days; Regimen-II: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then artemether (150 mg) plus pyrimethamine (50 mg) on the second day, and placebo on the third day; Regimen-III: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then artemether (150 mg) plus pyrimethamine (50 mg) on the second and third days. All patients had a rapid initial response to treatments with 95% of parasitemia being cleared within the first 24 hours. PCT24hours and PCT48hours were similar among the three drug regimens (11 vs 4, 6 vs 12, and 9 vs 11 patients for a 1-day, 2-day, and 3-day combination regimen, respectively). Fever was cleared within 48 hours in all patients in either group. Transient mild nausea, vomiting and loss of appetite were found in a few patients during the first 2 days of treatment. Seven patients did not complete the 28 day follow-up period (5 vs 2 in a 1-day vs 2-day regimen), the reason for withdrawal was not associated with drug-related adverse effects. Only 53 patients were therefore qualified for the efficacy assessment. There was 15, 13 and 5 patients in a 1-day, 2-day and 3-day combination regimens, respectively, who had reappearance of the parasitemia between days 11 and 21. The cure rates of the 3 treatment groups were statistically significantly different (0, 27.8, and 75% for a 1-day, 2-day and 3-day combination regimen, respectively). Two patients developed P. vivax malaria on days 20 and 24. All of the isolates were highly resistant to pyrimethamine, with MIC of 10(-5) M. There is potential advantage of this combination therapy in reducing the dosage and treatment period of artemisinin derivative, which is therefore likely to improve complaince in clinical practice. The use of a 3-day combination regimen (300 mg artemether plus 100 mg pyrimethamine on the first day, then 150 mg artemether plus 50 mg pyrimethamine on the second and third days) seems to be a good alternative regimen to sulfadoxine/ pyrimethamine in areas where P. falciparum is sensitive to pyrimethamine eg in Africa.