Primaquine Prophylaxis Dosing
For primary prophylaxis (preventing initial infection), primaquine is dosed at 30 mg base (52.6 mg salt) daily, taken with food, starting 1-2 days before travel and continuing daily during exposure and for 3 days after leaving the malarious area. 1
Primary Prophylaxis Regimen
Daily dosing of 30 mg base (approximately 0.5 mg/kg) is the established prophylactic dose for preventing both P. falciparum and P. vivax malaria during travel to endemic areas 1
This regimen demonstrated 85-93% protective efficacy in clinical trials conducted across multiple endemic regions (Indonesia, Kenya, Colombia) 1
The major advantage is the short duration required after leaving endemic areas - only 3 days post-exposure compared to 4 weeks for other antimalarials 1
Primaquine can be started just 1-2 days before entering malarious areas, unlike mefloquine or chloroquine which require 1-2 weeks of pre-travel dosing 1
Terminal Prophylaxis (Preventing Relapse)
For preventing P. vivax and P. ovale relapses after exposure, the dose is 15 mg base (26.3 mg salt) daily for 14 days 2
This terminal prophylaxis is administered during the last 2 weeks of the standard 4-week post-exposure prophylaxis period 3
Terminal prophylaxis is particularly indicated for persons with prolonged exposure in endemic areas, such as missionaries and Peace Corps volunteers 3
Critical Safety Considerations
G6PD testing is mandatory before prescribing primaquine for prophylaxis due to dose-dependent hemolytic risk in G6PD-deficient individuals 4, 5
The prophylactic dose (30 mg base daily) carries higher hemolytic risk than single low-dose regimens and should never be given without confirmed normal G6PD status 4, 6
Primaquine is absolutely contraindicated in pregnant women and should not be used during lactation unless the infant's G6PD status is known to be normal 2
Among 151 subjects evaluated after 20-52 weeks of daily primaquine therapy, methemoglobinemia was mild (<13%, typically <6%) and transient 1
Practical Administration
Primaquine must be taken with food to minimize gastrointestinal side effects and optimize absorption 1
In clinical trials involving 339 subjects taking primaquine for 12-52 weeks, there was no greater risk of adverse symptomatic events compared to placebo recipients 1
The drug should be dosed at 0.5 mg/kg per day for adults and children over 8 years of age 1
Context: Distinction from Gametocytocidal Dosing
The single low dose of 0.25 mg/kg (adult dose 15 mg) used for blocking P. falciparum transmission is entirely different from prophylactic dosing and carries minimal hemolytic risk even without G6PD testing 7
This transmission-blocking dose should not be confused with the higher daily doses required for actual prophylaxis against infection 5, 7