Atovaquone is an antiparasitic and antimicrobial medication used primarily to prevent and treat a specific type of pneumonia in people with weakened immune systems, and in combination with another drug, to prevent and treat malaria. It also plays an important role in treating babesiosis, a tick-borne infection. Here’s what you need to know about each use and how the drug works in practice.
Pneumocystis Pneumonia (PCP)
The FDA-approved use of atovaquone on its own (sold as the brand Mepron) is for a lung infection called Pneumocystis jirovecii pneumonia, commonly known as PCP. This infection almost exclusively affects people with compromised immune systems, particularly those living with HIV/AIDS. Atovaquone is approved both for preventing PCP and for treating mild to moderate cases in adults and adolescents 13 and older.
It’s not the first-choice drug for PCP. A combination antibiotic called trimethoprim-sulfamethoxazole (TMP-SMX) is the gold standard, but many people can’t tolerate it due to allergic reactions or side effects. Atovaquone serves as an alternative for those patients. Its efficacy for PCP prevention is rated as moderate compared to TMP-SMX, but it’s generally better tolerated. One practical advantage: it likely offers some protection against toxoplasmosis, another opportunistic infection common in immunocompromised people. It does not, however, protect against bacterial infections the way TMP-SMX does.
For PCP prevention, the standard dose is 1,500 mg of oral suspension taken once daily with food. Atovaquone has not been studied for severe PCP cases, so it’s reserved for mild to moderate infections.
Malaria Prevention and Treatment
When combined with proguanil (sold together as Malarone), atovaquone becomes one of the most commonly prescribed medications for travelers heading to malaria-endemic regions. This combination works against Plasmodium falciparum, the most dangerous malaria parasite.
For prevention, you start taking it one to two days before entering a malaria zone, continue daily throughout your stay, and keep taking it for one week after you return. That’s a shorter tail compared to some other antimalarials, which require four weeks of continued use after travel. Adults and anyone weighing more than 40 kg take one adult tablet daily. Children are dosed by weight, starting from 11 kg.
For treating an active malaria infection, adults take four tablets once daily for three days. Pediatric dosing follows a weight-based scale. The combination is effective against uncomplicated malaria caused by P. falciparum or unknown species, but it’s not used for severe malaria requiring hospitalization.
Babesiosis
Atovaquone paired with azithromycin is the preferred treatment for babesiosis, an infection caused by Babesia parasites transmitted through tick bites. The CDC recommends 750 mg of atovaquone taken orally twice daily alongside azithromycin for a standard course of 7 to 10 days. Immunocompromised patients often need longer treatment.
In people with healthy immune systems, symptoms typically resolve and the parasite clears from the blood during that standard treatment window. Fatigue and traces of the parasite detectable by sensitive lab tests may linger for several weeks, but actual relapse is unusual. For hospitalized patients with severe babesiosis, the same atovaquone dose is used but azithromycin is given intravenously rather than by mouth.
Why Food Matters With Atovaquone
Atovaquone is unusually dependent on food for absorption. Taking it with a fatty meal increases the amount of drug that actually reaches your bloodstream by two to three times compared to taking it on an empty stomach. Peak blood levels jump even more dramatically, roughly fivefold. If you take atovaquone without food, you may not absorb enough for it to work properly. This is true for both the suspension and tablet forms.
One important detail: the oral suspension and the tablet form are not interchangeable. They produce different blood levels of the drug, so you shouldn’t substitute one for the other without guidance. If you’re using the suspension, shake the bottle gently before each dose and measure carefully with an oral syringe or measuring cup. Tablets can be crushed if swallowing them whole is difficult.
Common Side Effects
Side effects depend on what you’re taking atovaquone for and which formulation you’re using. When used to treat malaria (as part of the combination with proguanil), the most frequently reported issues in adults are abdominal pain (17%), nausea (12%), vomiting (12%), and headache (10%). Diarrhea, weakness, loss of appetite, and dizziness each affect roughly 5 to 8% of people. Children tolerate it better overall, with vomiting (10%) and itching (6%) being the main complaints.
For malaria prevention, side effects are milder. In clinical trials, adults experienced stomach pain (4%), headache (4%), and gastritis (3%) at low rates. Vivid dreams occurred in 4 to 7% of people, and oral ulcers appeared in 4 to 6%. Children and adolescents taking it for prevention reported higher rates of abdominal pain (31%) and headache (14%) than adults.
When used alone for PCP prevention, the main side effects are gastrointestinal discomfort, rash, headache, and fever.
Who Should Not Take Atovaquone
The combination product with proguanil should not be taken by pregnant women, nursing mothers of infants under 5 kg, infants weighing less than 5 kg, or people with severe kidney disease. For atovaquone alone (Mepron), the same caution applies during pregnancy, as safety data is limited.
Several medications can significantly reduce atovaquone levels in the blood, potentially making it ineffective. Rifampin, rifabutin, and tetracycline all lower atovaquone concentrations and should not be taken at the same time. Metoclopramide, a drug commonly used for nausea and vomiting, also reduces atovaquone absorption and should be avoided, particularly when vomiting occurs during malaria treatment. People taking the blood thinner warfarin (Coumadin) may face an increased risk of bleeding when using atovaquone-proguanil, so that combination requires monitoring.