A 30-h in vitro susceptibility test of Plasmodium
falciparum wild isolates to artemisinin, chloroquine,
sulfadoxine/pyrimethamine and mefloquine was performed in Kibaha, Tanzania.
A sigmoid Emax model was fitted to all data for each
isolate and drug combination. Artemisinin and mefloquine exhibited 100% growth
inhibition against all isolates tested
(n=69–74). The EC50 values for artemisinin and
mefloquine were 44 and 146 nM respectively. Chloroquine and
sulfadoxine/pyrimethamine resistance was 30% and 13% respectively.
Susceptibility parameters (EC50,90,95 and
99 values and s) varied
between compounds and isolates indicating the different sensitivity of P.
falciparum isolates. No correlation between
susceptibility parameters of artemisinin and the other compounds was found.
The high in vitro activities of artemisinin
and mefloquine indicate their potential role for the treatment of
multidrug-resistant malaria in Africa.