Comparative efficiency of pyrimethamine-sulphormethoxine in malaria suppression given as single weekly, fortnightly...

2. One hundred and seventy inhabitants of the Ilorin area, Nigeria, were observed over a period of five months during the season of maximum malaria transmission while taking pyrimethamine-sulphormethoxine weekly, fortnightly and every four weeks. 2. There was no episode of malaria parasitaemia in the group receiving weekly doses of 25 mg. pyrimethamine and 0-5 mg. sulphormethoxine throughout the course of the trials. 3. There was one episode of asexual parasitaemia at the second month in the group receiving double fortnightly doses, but none by the third or fourth months. 4. The group receiving 75 mg. pyrimethamine and 1-5 mg. of sulphormethoxine had seven episodes of asexual parasitaemia throughout the course of the trial. 5. In all three groups there was no evidence of clinical acute malaria. 6. There were no appriciable side-effects in all groups within a follow-up period of four months. 7. The present trials confirm the advantage of the drug combination which proved to be more effective when given as weekly or fortnightly doses.