Primaquine: What It Is, How It Works, and What You Need to Know

When treating malaria, Primaquine, a synthetic 8-aminoquinoline antimalarial drug used to kill dormant liver stages of Plasmodium vivax and Plasmodium ovale. Also known as primaquine phosphate, it's one of the few medicines that can stop malaria from returning weeks or months after the initial infection. Most antimalarials only clear the parasites in your blood, but Primaquine goes after the hidden ones hiding in your liver. That’s why it’s called a radical cure—it doesn’t just treat the symptoms, it tries to end the whole infection for good.

But Primaquine isn’t for everyone. If you have G6PD deficiency, a genetic condition where your red blood cells break down too easily when exposed to certain drugs, taking Primaquine can cause severe anemia. Doctors always test for this before prescribing it. It’s not a risk you can ignore. Even if you feel fine, a simple blood test can save your life. And if you’re traveling to a place where malaria is common, knowing your G6PD status ahead of time makes all the difference.

Primaquine works alongside other drugs like chloroquine. While chloroquine clears the blood-stage parasites, Primaquine cleans up the leftovers in your liver. This combo is standard for malaria caused by Plasmodium vivax and Plasmodium ovale, which are the most common types to come back after treatment. Without Primaquine, up to 80% of people in some regions will have a relapse. That’s why it’s still used today, even with newer drugs on the market.

It’s also used in rare cases to stop the spread of malaria by killing the sexual forms of the parasite in the blood—so if you’re bitten by a mosquito, it won’t pick up the infection. That’s why public health programs sometimes give it to entire communities during outbreaks.

Side effects are usually mild—nausea, stomach upset, dizziness—but they can be worse if you’re not tested for G6PD deficiency. Some people report dark urine or feeling unusually tired, which are warning signs. If you’re on Primaquine, watch for those. Don’t assume it’s just a side effect—get checked.

There’s no sugarcoating it: Primaquine is powerful, but it’s also tricky. It’s not something you take casually. It’s not like a painkiller you grab off the shelf. It’s a targeted tool used under medical supervision. That’s why so many of the posts here focus on comparing antimalarials, checking drug interactions, and understanding patient safety. You won’t find a guide here that says, "Just take it if you feel sick." You’ll find ones that say, "Here’s how to do it right, and what to watch for."

What you’ll find below are real, practical comparisons and warnings from people who’ve been there—whether it’s how Primaquine stacks up against other radical cure options, what to do if you can’t tolerate it, or how to manage side effects without risking relapse. No fluff. Just what you need to know before you take the next step.