In-vitro activity of primaquine against the asexual blood stages of Plasmodium falciparum

The in vitro activities of dihydroartemisinin (the biologically active metabolite of artemisinin derivatives), chloroquine, monodesethylamodiaquine (the biologically active metabolite of amodiaquine), quinine, mefloquine, halofantrine, and pyrimethamine were assessed in 65 African isolates of #Plasmodium falciparum$ from Yaoundé, Cameroon using an isotopic microtest. The 50% inhibitory concentration (IC50) values for dihydroartemisinin were within a narrow range from 0.25 to 4.56 nM, with a geometric mean of 1.11 nM (95%) confidence interval = 0.96-1.28 nM). Dihydroartemisinin was equally active (P is greater than 0.05) against the chloroquine-sensitive isolates (geometric mean IC50 = 1.25 nM, 95% confidence interval ) 0.99-157 nM) and the chloroquine-resistant isolates (geometric mean IC50 = 0.979 nM, 95% confidence interval = 0.816-1.18 nM). A significant positive correlation was observed between the responses to dihydroartemisinin and mefloquine (r - 0.662) or halofantrine (r = 0.284), suggesting in vitro cross-resistance. There was no correlation between the responses to dihydroaertemisinin and other antimalarial drugs. ((Résumé d'auteur