Sensitivity of Plasmodium falciparum to chloroquine in Busia District, Kenya.

Individuals infected with Plasmodium falciparum were randomly divided into two groups; one group was treated with a single dose of 10 mg chloroquine base per kg. body-weight and the other with 25 mg base of chloroquine per kg body-weight given over three days, followed by an observation period of seven days. By Day 3 of observation complete parasite clearance had occurred in all the 125 triple dose recipients and 113 of 114 (99.1%) of those who had the single dose. 94.4% of 36 isolates tested in vitro by the macrotechnique were sensitive to drug concentration of 0.75 nmol/ml blood or less. On isolate was relatively less sensitive and required a concentration of chloroquine of 1.50 nmol/ml to inhibit schizont growth. However, the same isolate responded well to 25 mg base of chloroquine. These findings have demonstrated that, at present, isolates of P. falciparum in Busia District are sensitive to the standard dose of 10 mg chloroquine base and there is no reason therefore to resort to alternative antimalaria drugs. These should be reserved for special cases only.