Atovaquone
Other antiprotozoals
Other antiprotozoals
Oral suspension for Pneumocystis pneumonia and prophylaxis when trimethoprim-sulfamethoxazole cannot be used; with azithromycin it treats babesiosis.
Quick facts
- Group
- Other antiprotozoals
- Target
- Mitochondrial cytochrome bc1 complex (complex III), Qo site, of the parasite or fungus
- Used for
- Pneumocystis jirovecii pneumonia · Babesiosis
- Key effects
- Nausea · Headache and dizziness · Rash
- Monitor
- Clinical response · Diarrhoea or vomiting · Rash
- ATC
- P01AX06
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows atovaquone at the Qo site of yeast (Saccharomyces cerevisiae) cytochrome bc1, a model for the Pneumocystis and Plasmodium complexes.
A hydroxynaphthoquinone that imitates ubiquinone (coenzyme Q). It binds the Qo site of cytochrome bc1 in the microorganism's mitochondria, stops electron transport and collapses the membrane potential. In Plasmodium this also cuts off pyrimidine synthesis, which depends on the bc1 complex. It is selective because the microbial cytochrome b differs from the human one. Single changes in cytochrome b cause resistance.
- Imitates ubiquinone
- Binds the Qo site of cytochrome bc1
- Electron transport and membrane potential collapse
- The microorganism runs out of energy and pyrimidines
Indications
- Pneumocystis jirovecii pneumonia in teenagers and adults, and its prevention in people who cannot take another preventive drug (usually trimethoprim-sulfamethoxazole) Pneumocystis pneumonia (PCP) →
- Babesiosis, with azithromycin Babesiosis →
- Toxoplasmosis, as an alternative regimen Toxoplasmosis →
- Malaria, only in fixed combination with proguanil (see atovaquone + proguanil) Malaria →
Adverse effects
Common
- Nausea, vomiting and diarrhoea
- Headache and dizziness
- Rash
- Insomnia and anxiety
- Transient rises in liver enzymes or amylase
Contraindications
- Hypersensitivity to atovaquone
- Caution: severe gut disorders or diarrhoea that limit absorption; liver disease
Key interactions
- Rifampicin and rifabutin
- Lower atovaquone levels; the combination is avoided or monitored
- Tetracycline
- Lowers atovaquone concentrations
- Drugs highly bound to plasma proteins
- Atovaquone may compete for binding sites
What is monitored
- Clinical response (fever, oxygen saturation, breathing) in Pneumocystis pneumonia
- Diarrhoea or vomiting that may reduce absorption
- Rash
- Liver function in liver disease
Administration and safety
- Oral suspension, shaken gently before each use and measured with a proper dosing spoon or cup.
- Always given with meals (fat improves absorption).
- Vomiting and diarrhoea reduce absorption and can cause treatment failure: report them to the prescriber.
Pregnancy and breastfeeding
Safety in pregnancy and breastfeeding still needs further study; it is used only when the prescriber judges the benefit worth it.
Nursing care
- Give with food and check that meals are being eaten; fasting patients absorb it poorly.
- Record diarrhoea and vomiting and report them, since they can cause treatment failure.
- Watch breathing and oxygen saturation in pneumonia.
- Teaching: finish the course; tell the prescriber about rifampicin, rifabutin or antiretrovirals.
Pharmacokinetics
- Absorption
- Slow and variable; much better with a fatty meal
- Distribution
- More than 99 % bound to plasma proteins; very low levels in cerebrospinal fluid
- Metabolism
- Double peaks in the blood after a dose suggest enterohepatic cycling
Test yourself
Think of the answer, then tap the question to see it.
What is atovaquone's main indication?
Mild to moderate Pneumocystis jirovecii pneumonia and its prevention in people who cannot take trimethoprim-sulfamethoxazole.
Why must the suspension be given with food?
Its absorption is slow and variable and much better with fat; low levels lead to treatment failure.
Which drug is combined with atovaquone for babesiosis?
Azithromycin.
Connections
← Back to the class: Other antiprotozoals
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Atovaquone: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Structural analysis of atovaquone-inhibited cytochrome bc1 complex reveals the molecular basis of antimalarial drug action. (RCSB Protein Data Bank (entry 4PD4), 2015).
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Representative model, for educational purposes only.