Oseltamivir
Oseltamivir phosphate is an antiviral prodrug whose active metabolite targets influenza neuraminidase. Veterinary investigations have included experimental equine influenza and adjunctive treatment of canine parvoviral enteritis. These applications have different biological rationales: parvovirus lacks the influenza neuraminidase target, and clinical benefit in parvoviral enteritis remains unestablished.
Group
Neuraminidase inhibitor antiviral
Mechanism of Action
Conversion to oseltamivir carboxylate produces an inhibitor of influenza neuraminidase. Blocking cleavage of terminal sialic-acid residues impairs release and spread of newly formed influenza virions. Proposed effects in canine parvoviral enteritis involve secondary microbial or mucosal processes rather than direct inhibition of parvovirus replication; those proposed pathways and their clinical contribution remain uncertain.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Investigational parvoviral enteritis adjunct | 2 mg/kg | PO | Every 12 h | Up to 5 days; Studied with standard supportive therapy; no established improvement in mortality or hospitalization. This is not specific anti-parvoviral treatment. |
| Alternative investigational parvoviral enteritis adjunct | 2.2 mg/kg | PO | Every 12 h | Up to 5 days; Start early; give after effective antiemesis when needed to retain an oral dose. Benefit is not established and standard supportive care remains essential. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Experimental influenza A treatment | 2 mg/kg | PO | Every 12 h | Up to 5 days; Early-treatment experimental course derived from pediatric dosing; equine PK suggests intervals under 10 hours may be needed, so this is not a proven optimal exposure schedule. |
| Experimental influenza A prophylaxis | 2 mg/kg | PO | Every 24 h | Up to 5 days; Experimental exposure regimen; optimal duration and interval were not established. Not a routine prophylaxis recommendation. |
Indications
- Investigational adjunctive treatment of canine parvoviral enteritis alongside supportive care, with no established overall clinical advantage in the available controlled trial.
- Experimental treatment of equine influenza A infection to reduce selected clinical signs or viral shedding, with limited clinical field evidence.
Contraindications
- Hypersensitivity
Interactions
- Probenecid can increase exposure to the active metabolite by reducing renal secretion.
- May reduce response to live influenza vaccines; this is not expected with killed vaccines.
Adverse effects
- Possible gastrointestinal intolerance
Toxicity
Veterinary overdose thresholds are not established; provide supportive care and assess renal function and formulation ingredients.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Oseltamivir phosphate capsules 75 mg oseltamivir equivalent 75 mg oseltamivir free-base equivalent, supplied as phosphate. Whole-capsule administration may not suit the prescribed animal dose. | Capsule | 75 mg / capsule | PO |
| Tamiflu capsules 30 mg oseltamivir equivalent Oseltamivir free-base equivalent from phosphate; not the total phosphate salt mass. | Capsule | 30 mg / capsule | PO |
| Tamiflu capsules 45 mg oseltamivir equivalent Oseltamivir free-base equivalent from phosphate; not the total phosphate salt mass. | Capsule | 45 mg / capsule | PO |
Monitoring and Administration
Fluids, antiemesis, nutrition and other indicated supportive treatment remain central to parvoviral care.
In a blinded trial, treated dogs maintained leukocyte counts and gained weight, but hospitalization, disease severity and mortality were not significantly improved. Avoid presenting the investigational regimen as established curative therapy.
Assess severe renal impairment before dosing. Neonatal safety is uncertain; high-dose neonatal rat findings cannot be used to assert newborn puppy safety.
Capsules are expressed as oseltamivir base equivalents. Oral suspensions have differed by presentation: a historical 12 mg/mL product must not be confused with later lower-strength formulations. Verify actual bottle concentration and its reconstitution/storage instructions.