Consideration of ethics in primaquine therapy against malaria transmission.

Millions of people receive primaquine against sexual plasmodia responsible for malaria transmission. These gametocytes cause no symptoms and do not threaten the host, but they infect mosquitoes and threaten the community. Primaquine causes hemolysis in the small minority of patients with glucose-6-phosphate dehydrogenase deficiency (G6PDd). Clinical studies in the 1950s demonstrated gametocytocidal primaquine to be safe without G6PDd screening. However, the evaluated G6PDd variant, African A-, represents mild sensitivity to primaquine. The view of primaquine as a safe gametocytocide thus rests largely upon observations from a G6PDd variant that is unlikely to challenge safety. The early clinical work does not seem to afford an adequate assessment of safety in G6PDd patients. Potential risk of harm without clinical benefit to the patient raises ethical questions that should be examined.