Doxycycline prophylaxis for falciparum malaria.

188 schoolchildren aged 10-15 living in a malaria endemic area along the Thai-Burmese border were matched for age, splenomegaly, and weight and were then randomly assigned to receive either doxycycline (adult equivalent of 100 mg daily) or chloroquine (adult equivalent of 300 mg base weekly). All drugs were administered by the investigators and blood smears were done weekly. In 95 subjects taking doxycycline for 597 man-weeks there were 5 cases of falciparum malaria and in the 93 controls taking chloroquine for 488 man-weeks there were 31. Doxycycline was more effective than chloroquine in the prevention of falciparum malaria infections (p less than 0.0001). The doxycycline group did not have significantly more side-effects than the chloroquine group.