Adequate primaquine for vivax malaria.

BACKGROUND Treatment of vivax malaria with primaquine prevents the relapse of infection from residual liver stages of the parasite. Inadequate dosage is related to a higher relapse risk. METHODS A comparison was made of vivax malaria relapse-prevention treatments with primaquine 22.5 mg or 30 mg daily for 14 days on 146 reports to the Australian Army Central Malaria Register. RESULTS The lower dose of primaquine was found to carry a relative risk of 6.63 for a relapse of vivax malaria compared with the higher dose. CONCLUSIONS The available data presented here suggest that vivax malaria in this region is increasingly tolerant of the 22.5 mg daily treatment regimen of primaquine and that the greater dose of at least 30 mg daily is more effective.