Comparative efficacy of alternative primary therapies for Plasmodium falciparum infections in Malawi.

In Malawi, where high levels of chloroquine resistance were shown using a modified 7-day in vivo test, amodiaquine and pyrimethamine-sulfadoxine were evaluated as alternative initial therapies for Plasmodium falciparum infections in children under 5 years old. Therapy success rates, judged by parasite clearance by day 7 after initiation of therapy, were significantly greater among 39 children treated with amodiaquine at 10 mg/kg (90%), 37 receiving amodiaquine at 25 mg/kg (97%), and 34 receiving pyrimethamine-sulfadoxine (100%) at a dose of 25 mg sulfadoxine/kg, than among those treated with chloroquine at a dose of 25 mg/kg (59%) (P = 0.01). Extension of the follow-up period of those receiving amodiaquine (25 mg/kg) and pyrimethamine-sulfadoxine to 21 d revealed a progressively increasing rate of parasite recrudescence in the amodiaquine group (34%), but no recrudescence in the pyrimethamine-sulfadoxine group. These results suggest that, in Malawi, amodiaquine and pyrimethamine-sulfadoxine are superior to chloroquine in producing prompt clearance of P. falciparum parasites among young children, and that pyrimethamine-sulfadoxine alone is superior to the 4-aminoquinolines in sustaining P. falciparum clearance.