Primaquine: The Ultimate Guide to Its Uses, Benefits, and What You Need to Know

Primaquine isn’t a drug you hear about every day, but if you’ve traveled to a malaria-prone region or been treated for a specific type of malaria, it might have saved your life. Unlike other antimalarials that target the blood stage of the parasite, primaquine goes after the hidden reservoirs-those dormant liver forms that can wake up weeks or months later and cause a relapse. That’s why it’s not just another pill in the malaria toolbox. It’s the final piece many people miss.

What primaquine actually does

Primaquine is an 8-aminoquinoline antimalarial. It works by killing the Plasmodium vivax and Plasmodium ovale parasites that hide in the liver after an initial infection. These are the strains that cause relapses-sometimes months after you’ve left a tropical country and thought you were in the clear. Most antimalarials like chloroquine or atovaquone-proguanil clear the parasites from your bloodstream, but they don’t touch the liver stage. Primaquine does. That’s its superpower.

It’s also used in combination with artemisinin-based therapies to kill the sexual forms of Plasmodium falciparum, the deadliest malaria parasite. By stopping these forms, primaquine helps prevent the spread of malaria from person to person via mosquitoes. This makes it a critical tool in global malaria elimination efforts, especially in places like Southeast Asia and parts of Africa where drug-resistant strains are rising.

Who needs primaquine and when

You don’t take primaquine unless you’ve been diagnosed with P. vivax or P. ovale malaria, or if you’re being treated for P. falciparum in a setting where transmission blocking matters. It’s not a preventive drug like doxycycline or mefloquine. You only take it after infection.

For relapse prevention, the standard dose is 15 mg (base) once daily for 14 days. That’s 26.3 mg of the phosphate salt. The treatment starts after the blood-stage infection has been cleared with another drug like chloroquine. Skipping primaquine after treating vivax malaria is like turning off the alarm but leaving the burglar in the house. You might feel fine now, but the parasites are still waiting.

In areas where falciparum malaria is common and drug resistance is a problem, a single 0.75 mg dose of primaquine is added to artemisinin combination therapy. This single dose reduces transmission by up to 80% in some studies, according to WHO guidelines from 2024. It’s a small amount, but it makes a big difference in stopping outbreaks.

Why primaquine can be dangerous

Primaquine isn’t safe for everyone. The biggest risk is hemolytic anemia in people with G6PD deficiency-a genetic condition where red blood cells can’t handle oxidative stress. Primaquine triggers this stress. If you have G6PD deficiency and take primaquine, your red blood cells can break down rapidly, leading to jaundice, dark urine, fatigue, and in severe cases, kidney failure or death.

That’s why testing for G6PD deficiency is mandatory before prescribing primaquine in most countries. In places like Papua New Guinea, Thailand, and parts of Ethiopia, up to 15-20% of the population has some form of G6PD deficiency. In the U.S., it’s less common but still present, especially in people of African, Mediterranean, or Southeast Asian descent. If you’ve ever had unexplained anemia or jaundice as a child, you should get tested before even considering primaquine.

Other side effects are milder but still common: nausea, stomach cramps, dizziness, and headaches. These usually go away after a few days. But if you start feeling unusually tired, your skin turns yellow, or your urine becomes tea-colored, stop taking it and get medical help immediately.

How it compares to other antimalarials

Let’s say you’re back from a trip to Cambodia and you test positive for P. vivax. Your doctor gives you chloroquine to clear the blood infection. That’s step one. But without primaquine, you have a 70-80% chance of relapsing within six months. That’s not a risk most people are willing to take.

Some newer drugs like tafenoquine (Krintafel) can do the same job as primaquine in a single dose. But tafenoquine is more expensive, harder to get outside the U.S. and Australia, and still requires G6PD testing. Primaquine remains the most widely available, cost-effective option globally. It costs less than $1 for a full 14-day course in many low-income countries.

Here’s how they stack up:

For most travelers and health systems, primaquine still wins on accessibility and price. Tafenoquine is a good alternative if you struggle with adherence, but it’s not a replacement for primaquine in global programs.

What to do if you’re prescribed primaquine

If your doctor prescribes primaquine, here’s what you need to do:

1. Confirm you’ve had a G6PD test. If not, ask for one before taking the first pill.
2. Take it with food to reduce nausea. A light meal helps.
3. Finish the full 14-day course-even if you feel fine after day 5.
4. Watch for signs of anemia: pale skin, shortness of breath, dark urine.
5. Don’t drink alcohol while on primaquine. It increases liver stress.
6. Keep your follow-up appointment. Your doctor may want to check your blood count after treatment.

Some people worry about long-term effects. There’s no evidence primaquine causes lasting damage when used correctly. The risks come from skipping G6PD testing or stopping early. Don’t guess. Test. Finish. Stay safe.

Who should never take primaquine

Primaquine is off-limits in these cases:

• You have G6PD deficiency (confirmed or suspected)
• You’re pregnant (it can harm the fetus)
• You’re breastfeeding and your baby has G6PD deficiency (it passes into breast milk)
• You have active systemic infections like sepsis or severe liver disease
• You’re allergic to 8-aminoquinolines

If you’re a woman of childbearing age, your doctor should ask about pregnancy before prescribing. If you’re breastfeeding, your baby’s G6PD status matters too. In many regions, newborn screening includes G6PD testing-so ask your pediatrician if you’re unsure.

Why primaquine still matters in 2025

Despite newer drugs and better diagnostics, primaquine remains irreplaceable. The World Health Organization still lists it as an essential medicine. In 2024, over 12 million courses were distributed globally, mostly in sub-Saharan Africa and Southeast Asia. It’s the backbone of malaria elimination programs because it breaks the cycle of relapse and transmission.

Even with rising resistance to chloroquine in vivax malaria, primaquine remains effective. Its mechanism of action-damaging the parasite’s mitochondria-isn’t easily bypassed by mutations. That’s why researchers are now looking at combining it with new drugs to shorten treatment time. But for now, the 14-day course is still the gold standard.

For travelers, it’s not glamorous. No one wants to take a two-week course of pills after a vacation. But if you’ve been to Indonesia, the Amazon, or the Solomon Islands, skipping primaquine is like ignoring a warning light on your car’s dashboard. You might drive for months without trouble-but eventually, something will break.

Frequently Asked Questions

Next steps if you’re considering primaquine

If you’ve recently traveled to a malaria zone and are wondering whether you need primaquine, don’t guess. Get tested for malaria first. If the test is positive for P. vivax or P. ovale, ask your doctor about G6PD testing and whether primaquine is right for you. If you’re planning a trip to a high-risk area, talk to a travel clinic. They can help you choose the right combination of prevention and treatment options.

Primaquine isn’t flashy, but it’s one of the most precise tools we have against a disease that still kills over 600,000 people a year. Used correctly, it stops relapses. Used incorrectly, it can cause harm. Knowledge is your best protection. Test. Follow. Finish.