Atovaquone
**Atovaquone** is a highly lipophilic, synthetic hydroxynaphthoquinone antiprotozoal agent. In veterinary medicine, it has revolutionized the treatment of specific, notoriously difficult-to-treat tick-borne protozoal infections. **Key Clinical Uses:** * ***Babesia gibsoni* in Dogs:** Used synergistically with azithromycin. *B. gibsoni* is a small piroplasm that is often refractory to traditional therapies like imidocarb dipropionate. The atovaquone/azithromycin combination is currently the treatment of choice. * ***Cytauxzoon felis* in Cats:** Used in combination with azithromycin. Cytauxzoonosis is a highly fatal tick-borne disease in cats; this drug combination, alongside aggressive supportive care (IV fluids, heparin), has significantly improved survival rates. * **Pneumocystosis in Dogs:** Serves as a second-line therapy for *Pneumocystis* pneumonia when potentiated sulfonamides (like trimethoprim-sulfa) cannot be used or are ineffective. > **Clinical Pearl:** Atovaquone is generally well-tolerated as a single agent or with azithromycin, but it is notoriously expensive. The human combination drug Malarone® (atovaquone/proguanil) should **not** be substituted in dogs, as the proguanil component causes severe gastrointestinal toxicity.
Mecanismo: Atovaquone acts as a selective and potent inhibitor of the protozoan mitochondrial electron transport chain. * It acts as a structural analogue of ubiquinone (Coenzyme Q). * It binds to the ubiquinol oxidation pocket of the **cytochrome bc1 complex** (Complex III) in the protozoan inner mitochondrial membrane. * This binding blocks electron transfer → collapses the mitochondrial membrane potential → halts the function of **dihydroorotate dehydrogenase**, an enzyme critically dependent on electron transport. * Inhibition of this enzyme prevents *de novo* pyrimidine synthesis. Because these specific protozoa lack the ability to salvage preformed pyrimidines from their host, they cannot synthesize DNA or RNA, leading to parasite death.
Dosificación por especie
- Cytauxzoonosis (Cytauxzoon felis) · 15 mg/kg PO q8h · PO · q8h · Not specified · Give with azithromycin 10 mg/kg PO q24h. All cases were treated with IV fluids and most received heparin.
- Babesia gibsoni (Asian genotype) infections · 13.3 mg/kg PO q8h · PO · q8h · 10 days · Give with Azithromycin 10 mg/kg PO once daily. Reserve immunosuppressive therapy for cases that are not rapidly responding (3-5 days) to anti-protozoal therapy.
- Pneumocystosis · 15 mg/kg PO once daily · PO · q24h · 3 weeks · Considered second line therapy after potentiated sulfonamides.
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- Patients with a known hypersensitivity to atovaquone
- Patients with severe malabsorption syndromes
- Patients who cannot tolerate oral intake or cannot take the drug with a high-fat meal
Efectos adversos
- Gastrointestinal upset (nausea, vomiting, diarrhea)
- Rashes or hypersensitivity reactions
- Elevated liver enzymes
- CNS effects (headache, dizziness in humans)
- Fever
- Neutropenia and anemia (rare)
Interacciones farmacológicas
- Metoclopramide · Can decrease atovaquone plasma concentrations
- Tetracycline · Can decrease atovaquone plasma concentrations
- Rifampin · Can decrease atovaquone plasma concentrations
Monitoreo
- Clinical signs of efficacy (resolution of fever, lethargy, anemia)
- Serial CBCs to monitor anemia and platelet counts
- BUN, liver enzymes, and serum potassium (hypokalemia) in severe cases
- PCR testing at 60 days and 90 days post-therapy to confirm 'clearing' of B. gibsoni
Sobredosis
Limited information is available for any species regarding acute toxicity. Minimum toxic doses have not been established; laboratory animals have tolerated massive doses up to 31.5 grams without lethal effect. If an overdose occurs, treatment should be **symptomatic and supportive**. Due to high protein binding, dialysis is unlikely to be effective.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.