Malarone Drug Interactions: What to Avoid and What to Tell Your Doctor

Before you start taking Malarone (atovaquone/proguanil) for an upcoming trip, it's important to review your full medication list with your doctor or pharmacist. While Malarone has fewer drug interactions than some other antimalarials, several combinations are clinically significant — including some that can make Malarone less effective or significantly affect other medications you depend on.

Major Interactions to Discuss With Your Doctor

Warfarin and Coumarin-Based Anticoagulants (Blood Thinners)

The proguanil component of Malarone may potentiate (amplify) the anticoagulant effect of warfarin and other coumarin-based blood thinners. This can increase your bleeding risk. The exact mechanism of this interaction is not fully understood.

What to do: If you take warfarin, your doctor should closely monitor your INR (coagulation test) when starting or stopping Malarone. Don't skip this monitoring — a significantly elevated INR can lead to dangerous bleeding.

Efavirenz (HIV Medication)

Efavirenz (a common HIV antiretroviral medication, found in Sustiva, Atripla, and others) significantly decreases the blood levels of both atovaquone and proguanil. This interaction can render Malarone ineffective against malaria.

What to do: Avoid combining efavirenz with Malarone. If you are HIV-positive and taking an efavirenz-based regimen, discuss antimalarial alternatives with your doctor. Doxycycline or mefloquine (if not contraindicated by your HIV medications) may be safer options.

Rifampin and Rifabutin (Antibiotics for TB/Other Infections)

Rifampin (rifampicin) and rifabutin are powerful enzyme inducers that significantly reduce atovaquone plasma concentrations. Taking these with Malarone can dramatically lower Malarone blood levels to the point of therapeutic failure.

What to do: Concomitant use of rifampin or rifabutin with Malarone is not recommended. If you are taking either of these antibiotics (for tuberculosis, non-tuberculous mycobacteria, or other infections), discuss alternative antimalarial options with your prescriber.

Tetracycline Antibiotics

Tetracycline has been shown to reduce plasma concentrations of atovaquone by approximately 40%. While this is less severe than the rifampin/efavirenz interaction, it's clinically significant enough to require monitoring.

What to do: If you're taking tetracycline (not doxycycline, which is a different drug), alert your doctor. Monitoring of parasitemia is recommended if this combination cannot be avoided. Note that doxycycline itself is a separate antimalarial — if you're taking doxycycline for malaria prevention, you don't also need Malarone.

Metoclopramide (Nausea/Reflux Medication)

Metoclopramide (Reglan) may decrease the bioavailability of atovaquone by reducing absorption in the GI tract. This is a minor interaction, but it means Malarone may be less effective if you're relying on metoclopramide for nausea control.

What to do: Use other antiemetics (ondansetron, prochlorperazine) instead of metoclopramide if possible when taking Malarone.

Indinavir (HIV Protease Inhibitor)

Atovaquone has been shown to decrease trough (minimum) concentrations of indinavir by approximately 23%. This could potentially reduce the efficacy of your HIV treatment if indinavir levels fall below the therapeutic threshold.

What to do: If you're taking indinavir, discuss this interaction with your HIV specialist before starting Malarone.

Oral Typhoid Vaccine (Vivotif)

This is an important but commonly overlooked interaction for travelers: the proguanil component of Malarone has antibiotic-like activity that can inactivate the live attenuated bacteria in the oral typhoid vaccine (Vivotif). If you are getting the typhoid vaccine and Malarone at the same pre-travel visit, timing matters.

What to do: Complete your full Vivotif course (4 capsules over 7 days) and wait at least 10 days before starting Malarone. The injectable typhoid vaccine (Typhim Vi) is not affected — consider this if timing is tight.

Dapsone (Antibiotic)

Concurrent use of dapsone (topical or oral) with atovaquone or proguanil may increase the risk of hemolytic reactions (abnormal destruction of red blood cells). This combination should be avoided.

What to Tell Your Doctor Before Starting Malarone

Give your prescriber and pharmacist a complete list of all medications you take, including:

• All prescription medications (including HIV antiretrovirals, blood thinners, antibiotics)
• Over-the-counter medications (including antacids)
• Supplements and herbal products
• Any recent vaccines you received (especially Vivotif)

For a complete overview of Malarone's side effects beyond drug interactions, see our guide on Malarone side effects.

Once you've confirmed your medication list is clear and have your prescription, use medfinder to find which pharmacies near you have Malarone in stock.