Oseltamivir
**Oseltamivir** is a neuraminidase inhibitor antiviral primarily developed for the treatment and prophylaxis of **Influenza A and B** viruses in humans. In veterinary medicine, its use is highly controversial and largely experimental: - **Canine Parvovirus (CPV):** Anecdotally and in limited studies, it has been used as an adjunctive treatment for parvoviral enteritis. While it does not directly kill the parvovirus, it is theorized to reduce the virus's ability to penetrate the intestinal mucin layer and decrease secondary bacterial translocation. - **Equine Influenza:** Experimental studies have shown some efficacy in attenuating clinical signs, viral shedding, and secondary bacterial pneumonia when administered early. > **Public Health Warning:** Because oseltamivir (Tamiflu®) is a critical first-line defense for human influenza pandemics (e.g., H5N1), its use in veterinary patients is strongly discouraged by many experts (including the UC-Davis Koret Shelter Medicine Program) to preserve drug supplies and prevent the development of viral resistance. **Regulatory Note:** The FDA has strictly **banned** the extra-label use of oseltamivir and other influenza antivirals in chickens, turkeys, and ducks.
Mecanismo: Oseltamivir phosphate is a **prodrug** that is rapidly converted by hepatic esterases into its active metabolite, **oseltamivir carboxylate**. - **Antiviral Action:** It competitively inhibits the **viral neuraminidase enzyme** → prevents the cleavage of sialic acid residues on the host cell surface → halts the release of newly formed viral particles from infected cells and prevents viral aggregation. - **Parvovirus Mechanism (Theoretical):** Canine parvovirus does not possess neuraminidase. However, oseltamivir may inhibit host or bacterial neuraminidases in the GI tract → preserves the protective intestinal mucous layer → limits the ability of CPV to infect intestinal crypt cells and reduces GI bacterial colonization, translocation, and toxin absorption.
Dosificación por especie
- Treatment of equine Influenza A · 2 mg/kg PO twice daily for 5 days · PO · q12h · 5 days · Must be given early in the course of the disease to obtain satisfactory outcome. Dose based on human pediatric dosage.
- Adjunctive treatment of canine parvovirus enteritis · 2.2 mg/kg PO q12h · PO · q12h · Should be administered as early as possible in the course of the disease. More data is needed to prove efficacy.
- Adjunctive treatment of canine parvovirus enteritis · 2.2 mg/kg PO twice daily for 5 days · PO · q12h · 5 days · To better insure that a vomiting patient will keep the drug down, recommend administering it 30 minutes after a chlorpromazine or other antiemetic injection.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Known hypersensitivity to oseltamivir
- Poultry (chickens, turkeys, ducks) - FDA banned for extra-label use
Efectos adversos
- Gastrointestinal upset (nausea, vomiting - usually transient)
- Insomnia (reported in humans)
- Vertigo (reported in humans)
Interacciones farmacológicas
- Probenecid · May increase 2-fold the exposure to oseltamivir carboxylate (active metabolite) by reducing renal tubular secretion.
- Vaccines, influenza (live) · May potentially reduce the immune response to live influenza virus vaccines. No effect on inactivated (killed) vaccines.
Monitorización
- Clinical efficacy (resolution of clinical signs, weight gain, WBC count maintenance in parvo)
- Gastrointestinal tolerance
Sobredosis
Oseltamivir has a relatively **low toxic potential**. In humans, massive overdoses (up to 1000 mg) have primarily caused only gastrointestinal signs such as nausea and vomiting. Treatment should be supportive and symptomatic.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.