Mepron (atovaquone)
An approved treatment for Babesiosis.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Atovaquone wherever you encounter it, plus the key facts at a glance.
- Generic name
- Atovaquone
- Brand name
- Mepron
- Drug class
- Antiparasitic
- Manufacturer
- GlaxoSmithKline
- How it's taken
- For babesiosis, CDC's adult dosing table (adapted from the 2020 IDSA guideline) lists atovaquone 750mg by mouth twice a day, taken with azithromycin.
Atovaquone (Mepron) is a prescription oral liquid antiparasitic drug that doctors combine with the antibiotic azithromycin to treat babesiosis, a tick-borne infection of red blood cells[1][5].
- Mepron's FDA label covers only prevention and treatment of mild-to-moderate Pneumocystis pneumonia (PCP) in people 13 and older who cannot tolerate TMP-SMX, so atovaquone use for babesiosis is off-label[1].
- The 2020 IDSA guideline names atovaquone plus azithromycin the preferred babesiosis treatment for both outpatients and people hospitalized with severe disease[4].
- For babesiosis, CDC lists an adult atovaquone dose of 750mg by mouth twice a day with food, usually for at least 7 to 10 days[5].
- In a randomized trial of 58 people with babesiosis, atovaquone plus azithromycin worked as well as clindamycin plus quinine, with side effects in 15% versus 72%[6].
- Lyme-literate physicians describe Babesia infections that persist after standard atovaquone and azithromycin in some people with chronic Lyme symptoms[8].
- Richard Horowitz and colleagues report rotating antimalarial drugs, including atovaquone, and herbal therapies for these patients, based on chart reviews and case reports rather than randomized trials[8][9].
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How Atovaquone works
Atovaquone resembles ubiquinone (coenzyme Q), a molecule that cells use to make energy in their mitochondria[1]. In malaria parasites, the FDA label says atovaquone appears to act on the cytochrome bc1 complex, a step in that energy chain[1]. In Babesia microti, gene changes in the atovaquone-binding region of cytochrome b have been linked to relapsing infection, which points to a similar target[7].
Atovaquone is paired with azithromycin for babesiosis, and the IDSA guideline notes that resistance to either drug can emerge during long courses in highly immunocompromised patients[4].
Side effects and safety
Mepron has no boxed warning[1]. The label warns of liver injury, including hepatitis and fatal liver failure[1]. The label also warns of severe skin reactions such as Stevens-Johnson syndrome and DRESS, which can be life-threatening or fatal[1]. That skin warning was updated in March 2026, and the label instructs patients to stop taking Mepron immediately and promptly report the first sign of rash, mouth sores or other allergic signs[1].
In a PCP treatment trial against trimethoprim-sulfamethoxazole (TMP-SMX), the most common reactions to atovaquone tablets were rash (23% vs 34%), nausea (21% vs 44%) and diarrhea (19% vs 7%)[1]. Headache (16% vs 22%), vomiting (14% vs 35%) and fever (14% vs 25%) were also common[1]. Many people in those trials had advanced HIV, which the label says made it hard to tell drug reactions from illness[1]. Reports after approval include low platelets, methemoglobinemia (a blood oxygen problem), pancreatitis, kidney injury and corneal deposits[1].
In the babesiosis trial, diarrhea and rash were each reported by 8% of people taking atovaquone plus azithromycin[6].
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Atovaquone
For babesiosis, CDC's adult dosing table (adapted from the 2020 IDSA guideline) lists atovaquone 750mg by mouth twice a day, taken with azithromycin[5]. Outpatients take azithromycin 500mg on day 1 and then 250mg daily[5]. Hospitalized patients with severe disease get azithromycin 500mg by IV daily until symptoms improve, then switch to the oral doses[5].
Treatment usually lasts at least 7 to 10 days in total[5]. Highly immunocompromised patients may need 6 weeks or more, including 2 final weeks with no parasites seen on blood smears[4][5].
Mepron is a bright yellow, citrus-flavored suspension with 750mg in each 5mL, sold in bottles and single-dose foil pouches[1]. The label says to take it with food, because a meal raised blood levels about 2.6-fold in healthy volunteers[1]. CDC adds that a fatty meal is preferred[5]. The label reports that rifampin lowered atovaquone levels by about 52%, and that rifabutin, tetracycline and metoclopramide also lowered them[1].
The label's own dosing is for PCP in people aged 13 and older, and safety and effectiveness in children 12 and younger have not been established for that use[1]. CDC notes that clindamycin plus quinine, rather than atovaquone plus azithromycin, is generally recommended for symptomatic babesiosis during pregnancy unless the preferred drugs are unavailable or not tolerated[5].
Availability and cost
Generic versions may be available at a lower cost. Ask your pharmacist.
Help paying for Mepron
The maker of Mepron publishes no copay card; the offers below are what its official pages list. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE. People on Medicare may still qualify for the drugmaker's free medicine program. Without insurance, you can apply to the drugmaker's free medicine program, which sets its own eligibility rules. Pick your insurance below to see which offers fit you.
- Free medicine program
Free MEPRON for uninsured US or Puerto Rico residents with no prescription coverage who meet household income limits.
For: no insurance · source - Free medicine program
Free MEPRON for Medicare Part D patients who meet income limits and have spent $600 on prescriptions this calendar year.
For: Medicare · source
Good to know: Run by the GSK Patient Access Programs Foundation, a separate nonprofit. Covers the GSK brand (MEPRON) only, not generic versions. Income limits apply (48 states/DC: $47,880 for 1 person, $99,000 for 4). GSK's copay and coupon program lists do not include MEPRON. Generic atovaquone is widely available.
Clinical trial results
No trial has led to FDA approval of atovaquone for babesiosis[1]. The main babesiosis evidence is a 2000 NEJM randomized, nonblinded trial in 58 people with non-life-threatening Babesia microti infection[6]. Participants took atovaquone 750mg every 12 hours plus azithromycin (40 people) or clindamycin plus quinine (18 people) for 7 days[6].
Symptoms had resolved at 3 months in 65% versus 73% (p=0.66), and no parasites were found in anyone 3 months after treatment[6]. Side effects were reported by 15% on atovaquone plus azithromycin and 72% on clindamycin plus quinine (p<0.001)[6].
The IDSA guideline also cites a retrospective study of 40 hospitalized patients with severe babesiosis, 11 with life-threatening disease, treated only with atovaquone plus azithromycin[4]. IDSA described the combination as well tolerated and effective in that group[4].
Mepron's FDA approval rests on PCP trials, including a 408-person treatment trial against TMP-SMX and a 1,057-person prevention trial against dapsone[1].
Development history
The FDA first approved Mepron (atovaquone) tablets on November 25, 1992, as a new drug with orphan status for Pneumocystis pneumonia[2]. The oral suspension was approved on February 8, 1995, and the tablets are now discontinued[3][2].
Clindamycin plus quinine was the standard babesiosis treatment until a 2000 NEJM trial found atovaquone plus azithromycin as effective with fewer side effects[6]. The 2020 IDSA guideline named atovaquone plus azithromycin the preferred regimen[4]. In 2016, researchers linked relapsing Babesia microti infections to parasite gene changes where atovaquone binds[7]. In March 2026, GSK updated the Mepron label's warning on severe skin reactions[1].
Explore Babesiosis trials
Other Babesiosis treatments
Common questions about Atovaquone
▸What is Atovaquone (Mepron)?
Atovaquone (Mepron) is a prescription oral liquid antiparasitic drug that doctors combine with the antibiotic azithromycin to treat babesiosis, a tick-borne infection of red blood cells[1][5]. Mepron's FDA label covers only prevention and treatment of mild-to-moderate Pneumocystis pneumonia (PCP) in people 13 and older who cannot tolerate TMP-SMX, so atovaquone use for babesiosis is off-label[1]. The 2020 IDSA guideline names atovaquone plus azithromycin the preferred babesiosis treatment for both outpatients and people hospitalized with severe disease[4]. For babesiosis, CDC lists an adult atovaquone dose of 750mg by mouth twice a day with food, usually for at least 7 to 10 days[5]. In a randomized trial of 58 people with babesiosis, atovaquone plus azithromycin worked as well as clindamycin plus quinine, with side effects in 15% versus 72%[6]. Lyme-literate physicians describe Babesia infections that persist after standard atovaquone and azithromycin in some people with chronic Lyme symptoms[8]. Richard Horowitz and colleagues report rotating antimalarial drugs, including atovaquone, and herbal therapies for these patients, based on chart reviews and case reports rather than randomized trials[8][9].
▸How does Atovaquone work?
Atovaquone resembles ubiquinone (coenzyme Q), a molecule that cells use to make energy in their mitochondria[1]. In malaria parasites, the FDA label says atovaquone appears to act on the cytochrome bc1 complex, a step in that energy chain[1]. In Babesia microti, gene changes in the atovaquone-binding region of cytochrome b have been linked to relapsing infection, which points to a similar target[7]. Atovaquone is paired with azithromycin for babesiosis, and the IDSA guideline notes that resistance to either drug can emerge during long courses in highly immunocompromised patients[4].
▸What are the side effects of Atovaquone?
Mepron has no boxed warning[1]. The label warns of liver injury, including hepatitis and fatal liver failure[1]. The label also warns of severe skin reactions such as Stevens-Johnson syndrome and DRESS, which can be life-threatening or fatal[1]. That skin warning was updated in March 2026, and the label instructs patients to stop taking Mepron immediately and promptly report the first sign of rash, mouth sores or other allergic signs[1].
In a PCP treatment trial against trimethoprim-sulfamethoxazole (TMP-SMX), the most common reactions to atovaquone tablets were rash (23% vs 34%), nausea (21% vs 44%) and diarrhea (19% vs 7%)[1]. Headache (16% vs 22%), vomiting (14% vs 35%) and fever (14% vs 25%) were also common[1]. Many people in those trials had advanced HIV, which the label says made it hard to tell drug reactions from illness[1]. Reports after approval include low platelets, methemoglobinemia (a blood oxygen problem), pancreatitis, kidney injury and corneal deposits[1].
In the babesiosis trial, diarrhea and rash were each reported by 8% of people taking atovaquone plus azithromycin[6].
▸How is Atovaquone taken?
For babesiosis, CDC's adult dosing table (adapted from the 2020 IDSA guideline) lists atovaquone 750mg by mouth twice a day, taken with azithromycin[5]. Outpatients take azithromycin 500mg on day 1 and then 250mg daily[5]. Hospitalized patients with severe disease get azithromycin 500mg by IV daily until symptoms improve, then switch to the oral doses[5]. Treatment usually lasts at least 7 to 10 days in total[5]. Highly immunocompromised patients may need 6 weeks or more, including 2 final weeks with no parasites seen on blood smears[4][5].
Mepron is a bright yellow, citrus-flavored suspension with 750mg in each 5mL, sold in bottles and single-dose foil pouches[1]. The label says to take it with food, because a meal raised blood levels about 2.6-fold in healthy volunteers[1]. CDC adds that a fatty meal is preferred[5]. The label reports that rifampin lowered atovaquone levels by about 52%, and that rifabutin, tetracycline and metoclopramide also lowered them[1].
The label's own dosing is for PCP in people aged 13 and older, and safety and effectiveness in children 12 and younger have not been established for that use[1]. CDC notes that clindamycin plus quinine, rather than atovaquone plus azithromycin, is generally recommended for symptomatic babesiosis during pregnancy unless the preferred drugs are unavailable or not tolerated[5].
▸Is Atovaquone FDA approved?
Yes, Atovaquone (Mepron) is FDA approved (1992) for the treatment of Babesiosis.
▸Do Lyme-literate doctors use atovaquone differently for babesiosis?
Some Lyme-literate physicians use atovaquone as one part of longer, rotating treatment for what they describe as persistent babesiosis in people with chronic Lyme symptoms.
Who describes it: Richard Horowitz and colleagues write that Babesia can persist after standard atovaquone and azithromycin, and report rotating antimalarial drugs and herbal therapies[8][9].
Evidence: these reports come from chart reviews and case reports, not randomized trials[8][9].
Mainstream guidance: the 2020 IDSA guideline describes a set course of atovaquone plus azithromycin, with longer treatment for people who are highly immunocompromised[4].
Source: Horowitz and Freeman, Healthcare 2018; Horowitz, Fallon and Freeman, Microorganisms 2024; IDSA 2020.
▸What is atovaquone (Mepron) used for in babesiosis?
Atovaquone (Mepron) is not FDA-approved for babesiosis, but the 2020 IDSA guideline names it as part of the preferred treatment[4][1].
Mainstream guidance: The 2020 IDSA guideline names atovaquone plus azithromycin the preferred treatment for both mild-to-moderate and severe babesiosis[4].
Source: IDSA guideline, 2020; Mepron FDA label, Mar 2026
▸How does atovaquone work against Babesia?
Atovaquone resembles coenzyme Q, which cells use to make energy[1].
In malaria: In malaria parasites it appears to block the cytochrome bc1 complex, according to the FDA label[1].
In Babesia: In Babesia microti, mutations where it binds cytochrome b are linked to relapse, pointing to a similar target[7].
Source: Mepron FDA label, Mar 2026; Nature Microbiology, 2016
▸What are the side effects of atovaquone?
In a PCP treatment trial, the most common reactions to atovaquone included rash, nausea, diarrhea, headache, vomiting and fever[1].
Serious warnings: The label warns of liver injury, including fatal liver failure, and of severe skin reactions such as Stevens-Johnson syndrome and DRESS[1].
What the label asks: The label asks patients to promptly report the first sign of rash, mouth sores or other allergic signs to their doctor[1].
Source: Mepron FDA label, Mar 2026
▸How is atovaquone taken for babesiosis?
For babesiosis, CDC lists atovaquone 750mg by mouth twice a day with food plus azithromycin[5].
Length of treatment: CDC says treatment usually lasts at least 7 to 10 days[5]. Highly immunocompromised patients may need 6 weeks or more[5][4].
With food: The label says to take it with food, and CDC says a fatty meal is preferred[1][5].
Source: CDC, Clinical Care of Babesiosis; IDSA guideline, 2020; Mepron FDA label, Mar 2026
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- GlaxoSmithKline via DailyMed · 2026-03. MEPRON (atovaquone) oral suspension prescribing information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b426b6bf-f07e-4580-97ae-dfca1ddf5b8f
- FDA · 1992-11-25. Mepron (atovaquone) tablets, NDA 020259 approval history. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020259
- FDA · 1995-02-08. Mepron (atovaquone) oral suspension, NDA 020500 approval history. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020500
- Infectious Diseases Society of America · 2021-01. Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA): 2020 Guideline on Diagnosis and Management of Babesiosis. https://www.idsociety.org/practice-guideline/babesiosis/
- CDC · 2024-02-13. Clinical Care of Babesiosis (for health care providers). https://www.cdc.gov/babesiosis/hcp/clinical-care/index.html
- New England Journal of Medicine (via PubMed) · 2000-11-16. Atovaquone and azithromycin for the treatment of babesiosis. https://pubmed.ncbi.nlm.nih.gov/11078770/
- Nature Microbiology (via PubMed) · 2016-06-13. A global map of genetic diversity in Babesia microti reveals strong population structure and identifies variants associated with clinical relapse. https://pubmed.ncbi.nlm.nih.gov/27572973/
- Healthcare (Basel) · 2018-11-05. Precision Medicine: The Role of the MSIDS Model in Defining, Diagnosing, and Treating Chronic Lyme Disease/Post Treatment Lyme Disease Syndrome and Other Chronic Illness: Part 2. https://pmc.ncbi.nlm.nih.gov/articles/PMC6316761/
- Microorganisms · 2024-04-30. Combining Double-Dose and High-Dose Pulsed Dapsone Combination Therapy for Chronic Lyme Disease/Post-Treatment Lyme Disease Syndrome and Co-Infections, Including Bartonella: A Report of 3 Cases and a Literature Review. https://pmc.ncbi.nlm.nih.gov/articles/PMC11124288/