Sensitivity of falciparum malaria to chloroquine and amodiaquine in four districts of western Kenya (1985-1987).

In-vivo and in-vitro studies to determine the sensitivity of Plasmodium falciparum malaria to chloroquine and amodiaquine were conducted in 4 districts of Western Kenya over a 2-year-period. Patients aged 5-60 years, were treated with chloroquine or amodiaquine base 25 mg/kg over 3 days. Recurrence of parasitaemia within 7 days (R1 resistance) or failure to clear parasites (R11 resistance) was observed in 27% of infections in West Pokot district, 51% in Busia, 45% in Bungoma and 19% in Rusinga Island. R111 resistance (failure to decrease parasitaemia by at least 75%) was documented in Rusinga Island. The proportions of parasites with minimum inhibitory concentrations (MICs) for chloroquine greater than 114 nM in in-vitro tests ranged from 37% in Busia to 68% in Bungoma. For amodiaquine, 20% of 30 isolates tested had MICs greater than 80 nM. We conclude that resistance to chloroquine is now established in the area and amodiaquine may be useful in uncomplicated chloroquine resistant falciparum infections in the region.