What Is Primaquine? Uses, Dosage, and What You Need to Know in 2026

Primaquine is one of the oldest and most important antimalarial drugs in modern medicine — yet most people in the US have never heard of it. That's because malaria isn't a domestic disease in the United States. But for travelers to endemic regions and for patients who have returned with a specific type of malaria, primaquine may be a critical part of their treatment. Here's everything you need to know about primaquine in 2026.

What Is Primaquine?

Primaquine phosphate is a prescription antimalarial drug in the 8-aminoquinoline class. It was first synthesized in the 1940s and received FDA approval in 1952. It remains on the World Health Organization's List of Essential Medicines and is considered irreplaceable in the global fight against malaria.

In the US, primaquine is only available as a generic. There is no brand-name version. The tablet contains 26.3 mg of primaquine phosphate, which equals 15 mg of primaquine base — the biologically active form. Dosing is expressed in terms of the base.

What Is Primaquine Used For?

Primaquine has one FDA-approved indication and several important off-label uses:

Radical cure of Plasmodium vivax malaria (FDA-approved): This is primaquine's primary role. P. vivax creates dormant forms called hypnozoites that hide in the liver after the initial infection is cleared. Without radical cure, these hypnozoites can reactivate and cause a relapse weeks, months, or years later. Primaquine is one of only two FDA-approved drugs (along with tafenoquine) that eliminate hypnozoites.

Radical cure of Plasmodium ovale malaria: P. ovale, like P. vivax, forms hypnozoites. Primaquine is used off-label (but recommended by the CDC) for anti-relapse therapy in P. ovale infections.

Malaria prophylaxis (CDC-recommended, off-label): The CDC recommends primaquine as a prophylactic option for travelers to regions where P. vivax is predominant — particularly areas where chloroquine resistance makes other options less effective. Its key advantage in prophylaxis: it also provides "terminal prophylaxis" by clearing any hypnozoites acquired during travel, preventing post-travel relapse.

Pneumocystis pneumonia (PCP) treatment (off-label): In immunocompromised patients (particularly those with HIV/AIDS), primaquine combined with clindamycin is used as an alternative treatment for PCP when first-line therapy (trimethoprim-sulfamethoxazole) isn't tolerated.

Primaquine Dosage: How Much Do You Take?

Primaquine comes in one tablet strength: 26.3 mg (equivalent to 15 mg base). Dosing varies by indication:

Radical cure (P. vivax or P. ovale): 15-30 mg base (1-2 tablets) once daily for 14 days. The higher dose (30 mg/day) is used for severe cases or in regions with evidence of reduced primaquine sensitivity.

Prophylaxis (adults, per CDC): 30 mg base (2 tablets) once daily. Start 1-2 days before entering the malaria zone, continue throughout exposure, and take for 7 days after returning.

Pediatric dosing: 0.25-0.5 mg base/kg/day for 14 days (maximum 30 mg/day).

Modified regimen for mild-moderate G6PD deficiency: 45 mg base once weekly for 8 weeks with CBC monitoring. This extended, lower-intensity schedule is CDC-recommended for patients who can't receive standard daily dosing.

How Should I Take Primaquine?

Take with food. Always take primaquine with a meal or milk to minimize nausea and stomach upset — the most common side effects.

Same time each day. Take it at the same time each day to maintain consistent blood levels.

Complete the full course. Do not stop taking primaquine early, even if you feel well. Incomplete treatment may leave hypnozoites alive in the liver.

Avoid grapefruit juice. Grapefruit can increase primaquine blood levels by inhibiting the CYP3A4 enzyme that metabolizes it.

Who Should NOT Take Primaquine?

Pregnant women (risk of hemolysis in the fetus)

Patients with severe G6PD deficiency

Patients taking quinacrine (absolutely contraindicated — dangerous interaction)

Breastfeeding mothers when infant G6PD status is unknown or deficient

For a complete look at primaquine side effects and warnings, see our primaquine side effects guide. And if you're having trouble filling your prescription, medfinder can locate pharmacies near you that have primaquine in stock.