Response of falciparum malaria to chloroquine and three second line antimalarial drugs in a Kenyan coastal school age population.

Ambulatory rural school children in the Mombasa area with P. falciparum parasitaemia were examined and randomly assigned to treatment with one of three second-line antimalarials--amodiaquine, pyrimethamine/sulphadoxine (P/SD) and pyrimethamine/sulfalene (P/SL). Clinical signs and parasitaemia were followed daily for the first week and on days 14 and 28. WHO Mark II schizont inhibition tests were performed for all the above 3 drugs and chloroquine. The total number of cases was 73. The mean parasite density was 142.1 +/- 207; 102.7 +/- 166; 82.74 +/- 93 parasites per 300 WBC for amodiaquine, P/SD, and P/SL, respectively. In vitro tests showed a chloroquine resistance rate of 60% and no resistance to all of the second line drugs. Also, all children treated successfully cleared their parasitaemia with mean clearance rates of 2.05 +/- 0.57; 1.86 +/- 0.47; 2.05 +/- 0.50 days for amodiaquine, P/SD and P/SL, respectively. Even though, no difference in the effectiveness between the second line drugs used was found, reinfection rates as depicted by day 28 parasitaemia differed--amodiaquine 16%; P/SD 0%; and P/SL4.35%. This difference could be attributed to the difference in the pharmacokinetic properties of the drugs.