Chemoresistance of Plasmodium falciparum in the urban region of Yaounde, Cameroon. Part 2: Evaluation of the efficacy of amodiaquine and sulfadoxine-pyrimethamine combination in the treatment of uncomplicated Plasmodium falciparum malaria in Yaounde, Cameroon.

The spread of chloroquine resistance or its stabilization at a high level calls for a change in the therapeutic strategy, including a possible replacement of chloroquine. We assessed and compared the efficacy of amodiaquine and sulfadoxine-pyrimethamine in Yaoundé. Of 140 adults and children > 5 years enrolled in the study, 59 in the amodiaquine and 58 in the sulfadoxine-pyrimethamine treatment group were followed until day 14. The efficacy of amodiaquine was 100%, whereas 12.1% of the patients treated with sulfadoxine-pyrimethamine responded with an early treatment failure. Side effects in both treatment groups were mild and did not require any specific treatment. We did in vitro drug assays for monodesethylamodiaquine (active metabolite of amodiaquine) and pyrimethamine and measured plasma levels of monodesethylamodiaquine, sulfadoxine, and pyrimethamine. Unlike amodiaquine, the results of the in vitro drug sensitivity test for pyrimethamine were not concordant with the clinical response. A wide inter-individual variation in the plasma drug levels was observed. Unlike chloroquine, the mean plasma concentrations did not vary with age. There was no significant difference in the plasma concentrations of sulfadoxine and pyrimethamine between patients responding with an adequate clinical response and those responding with treatment failure. Amodiaquine has several advantages over sulfadoxine-pyrimethamine combination and may be considered to be an effective drug in an endemic zone with a moderate level of chloroquine resistance.