The relationship between the response of Plasmodium falciparum malaria to mefloquine in African children and its sensitivity in vitro.

The clinical efficacy of two doses of mefloquine (15 and 25 mg/kg body weight) was evaluated in 85 children suffering from acute symptomatic falciparum malaria. The cure rate on day 28 was 100% in both groups. There was no significant difference (P > 0.05) in the mean parasite and fever clearance times in both groups (48.5 +/- 14.6 and 32.0 +/- 12.7 h respectively for the 25 mg/kg group and 49.0 +/- 15.1 and 30.0 +/- 13.3 h respectively for the 15 mg/kg group). There was also no significant difference (P > 0.05) in these values between children with hyperparasitaemia (53.6 +/- 11.1 and 36.0 +/- 17.0 h respectively) and those without hyperparasitaemia (49.1 +/- 13.6 and 31.8 +/- 14.6 h respectively). Recurrence of parasitaemia was observed after day 30 in 2 patients in the 15 mg/kg group and in 1 patient in the 25 mg/kg group. In vitro, 3 of 21 isolates showed reduced susceptibility to mefloquine, with minimum inhibitory concentrations (MIC) > 67 nM/litre. The MIC and 50%, 90% and 99% inhibitory concentrations were 200.8, 6.27, 31.7 and 119.6 nM/litre respectively. Four of 22 isolates were resistant to chloroquine (MIC > 108 nM/litre). Isolates that showed low sensitivity to mefloquine in vitro were sensitive to chloroquine in vitro, and the 4 that were resistant to chloroquine were sensitive to mefloquine. Irrespective of MIC and dose of mefloquine, parasitaemia cleared in all subjects in 96 h or less.(ABSTRACT TRUNCATED AT 250 WORDS)