Primaquine Prophylaxis Dosing
For terminal prophylaxis to prevent P. vivax and P. ovale relapses after exposure, the CDC recommends primaquine 15 mg base (26.3 mg salt) daily for 14 days. 1
Indication for Terminal Prophylaxis
Terminal prophylaxis is specifically indicated for persons with prolonged exposure in malaria-endemic areas, such as missionaries and Peace Corps volunteers, to eradicate dormant liver-stage parasites (hypnozoites) that cause relapses. 1
This regimen should be administered after leaving the endemic area to prevent relapse, not during active exposure. 1
Alternative Primary Prophylaxis Regimen
For primary prophylaxis (prevention during exposure rather than terminal prophylaxis), primaquine 30 mg base (0.5 mg/kg) daily has demonstrated 85-93% protective efficacy against both P. falciparum and P. vivax in clinical trials. 2
The major advantage of primaquine for primary prophylaxis is that it does not require pre-travel dosing and only needs to be continued for 3 days after leaving the malarious area, unlike other antimalarials. 2
This higher dose (30 mg base daily) was well-tolerated in 339 subjects taking it for 12-52 weeks, with only mild, transient methemoglobinemia (<13%, typically <6%). 2
Critical G6PD Deficiency Screening Requirement
Primaquine is absolutely contraindicated without G6PD testing for these prophylactic regimens, as the cumulative 14-day course poses significant hemolytic risk in G6PD-deficient individuals. 3, 4
The 14-day radical cure regimen (total dose 3.5-7 mg/kg) carries substantially higher hemolytic risk than single low-dose regimens, with nearly all reported primaquine-related deaths occurring after multiple dosing. 5
G6PD deficiency affects 3-30% of populations in malaria-endemic regions, making screening essential before prescribing prophylactic courses. 4
Important Caveats
The single low dose of 0.25 mg/kg used for P. falciparum gametocytocidal effect is NOT the same as prophylaxis dosing and carries minimal hemolytic risk even without G6PD testing. 6
Primaquine should be taken with food to minimize gastrointestinal side effects and optimize absorption. 2
For radical cure of active vivax malaria, primaquine should be given concurrently with chloroquine to first eliminate blood-stage parasites. 3