G6PD and Plasmodium vivax malaria: In malaria prophylaxis, a 30 mg daily dose of primaquine has been shown to be well tolerated even when given continuously for as long as 20 weeks.2,3 For radical cure of vivax malaria in normal G6PD patients, adult doses of primaquine at 22.5 to 30 mg proved safe and effective in Thailand,4,5 and the higher dose (0.5 mg base/kg) has recently been recommended by the World Health Organization.