Efficacy of different primaquine-based antimalarial regimens against Plasmodium falciparum gametocytemia

This study compared the efficacy against Plasmodium falciparum gametocytes of four regimens: amodiaquine–sulfadoxine/pyrimethamine (AQ–SP) and mefloquine–artesunate (MQ–AS), with and without primaquine (PQ) administered with the second dose of the schizonticide (AQ–SP; AQ–SP–PQ; MQ–AS; MQ–AS–PQ). Efficacy was determined by thick smear on days 1, 4 and 8 after the beginning of treatment. A total of 82 patients (19–23/group) were recruited. After AQ–SP administration, gametocytemia steadily increased until day 8. With AQ–SP–PQ, a marked decline in gametocytemia was detected on days 4 and 8. MQ–AS treatment resulted in reduced gametocytemia on days 4 and 8, and with MQ–AS–PQ it was reduced even further. None of the treatments cleared gametocytemia by day 8. Currently, artemisinin-based combination therapies plus PQ are the recommended treatment option against falciparum malaria; however, further studies are required to optimize the use of PQ. Issues to be addressed include the optimal time of administration, treatment duration, optimal daily and total dose, and day of evaluation of the gametocytocidal effect. In falciparum malaria, the WHO recommends a maximum of 4 days of treatment; consequently, an effective regimen must clear asexual parasites and symptoms within this time frame. The same criteria should be taken into account when evaluating the anti-gametocyte activity.