In vitro susceptibility of Plasmodium falciparum to amodiaquine, mefloquine, quinine and chloroquine in Liberia, West Africa.

The in vitro susceptibility of seven Plasmodium falciparum isolates to four schizonticidal drugs was studied in Yekepa area, northern Liberia, by the Rieckmann 24-hour micro method. The seven patients were successfully treated with the standard chloroquine regimen. The results of the individual in vitro tests all indicated full susceptibility to the four drugs. By probit analysis, the drug concentrations achieving 50% (EC 50) and 99% (EC 99) inhibition, respectively, were 0.2 and 0.7 microM chloroquine, 0.04 and 0.2 microM amodiaquine, 0.01 and 0.07 microM mefloquine and 1.4 and 3.0 microM quinine.