Studies on the chemotherapy of malaria

Hospital trials of pyrimethamine, sulphormethoxine and dapsone were carried out in Gambian patients with overt malaria. Small single doses of pyrimethamine were effective in acute attacks of malaria but further treatment with pyrimethamine alone in some cases led to the emergence of resistant asexual falciparum parasites. Treatment with sulphormethoxine or dapsone alone was unsatisfactory but when combined with as little as 0·01 mg./kg. of pyrimethamine, a potent schizontocidal effect was sustained indicating a strong potentiating link in the action of these drugs in combination with pyrimethamine. Treatment with the adult equivalent of pyrimethamine 5 mg. and sulphormethoxine 100 or dapsone 50 mg. was completely effective in terminating acute attacks of falciparum malaria in susceptible children although the period of fever was prolonged after elimination of asexual parasitaemia in patients with high parasitaemias. Field trials with weekly or fortnightly doses with these combinations are advocated for malaria suppression in ‘semi-immunes’.