Primaquine Prophylaxis Dosing
For primary prophylaxis (prevention during exposure), the recommended dose is 30 mg base daily, while for terminal prophylaxis (prevention of relapse after exposure), the dose is 15 mg base daily for 14 days. 1, 2
Primary Prophylaxis (During Exposure)
- The dose for primary malaria prophylaxis is 30 mg base (0.5 mg/kg/day) taken daily with food 3, 4
- This regimen provides approximately 85-93% protective efficacy against both P. falciparum and P. vivax 4
- A major advantage is that primaquine can be discontinued within 3 days after leaving the malarious area, unlike other antimalarials that require 4 weeks of post-exposure dosing 4
- The drug should be started 1-2 days before entering the endemic area 3
Terminal Prophylaxis (Post-Exposure Relapse Prevention)
- The CDC recommends 15 mg base daily for 14 days as terminal prophylaxis to prevent P. vivax and P. ovale relapses after exposure 1, 2
- This regimen is particularly indicated for persons with prolonged exposure in endemic areas, such as missionaries and Peace Corps volunteers 1
- Terminal prophylaxis can be added during the last 2 weeks of the standard 4-week post-exposure period when travelers have been on other prophylactic agents like doxycycline 5
Critical Safety Considerations
- G6PD testing is mandatory before prescribing primaquine, as the drug causes dose-dependent hemolysis in G6PD-deficient individuals 5, 6
- Primaquine is absolutely contraindicated in pregnancy 5
- Taking primaquine with food minimizes gastrointestinal disturbances 3
- In clinical trials involving 339 subjects taking 30 mg base daily for 12-52 weeks, methemoglobinemia was mild (<13%, typically <6%) and transient 4
Common Pitfalls to Avoid
- Do not confuse the primary prophylaxis dose (30 mg base daily) with the terminal prophylaxis dose (15 mg base daily for 14 days) 1, 2, 3
- Never prescribe primaquine without confirming normal G6PD status, as mortality has been reported (estimated one in 621,428 treated patients) 7
- The FDA label specifies that primaquine should be given concurrently with chloroquine when treating acute vivax malaria to eradicate exoerythrocytic parasites 2