Sensitivity of Plasmodium falciparum to chloroquine in pregnant women in Zaria, northern Nigeria.

Thirty-five pregnant women with Plasmodium falciparum parasitaemia were treated with chloroquine 25 mg/kg body weight over 3 days. They were followed up in vivo by use of a modified 14-day WHO extended field test. In vitro sensitivity of the parasite isolates to chloroquine was assessed by using the WHO microtest method. All pregnant women were aparasitaemic by day 7 and there was no parasite reappearance throughout the 14-day observation period. The mean parasite clearance time (MPCT) was 3.2 +/- 1.4 days. Eleven parasite isolates obtained from the women were highly susceptible to chloroquine in vitro. The effective drug concentration that gave 99% parasite growth inhibition (EC 99) was 0.36 mumol/l.