Veterinary 2025 Guide: Ondansetron (Zofran®) for Nausea & Vomiting in Dogs & Cats 🐾🩺

Hello, I’m Dr Duncan Houston BVSc. This 2025 guide explores ondansetron—a 5-HT₃ serotonin antagonist used off-label as an antiemetic in dogs and cats. We will cover its uses (such as chemotherapy vomiting, parvovirus, vestibular disease, CKD-induced nausea), pharmacology, dosing protocols, side effects, contraindications, monitoring strategies, and client education—enhanced with Ask A Vet support 😊.

🔎 1. What Is Ondansetron?

Ondansetron blocks serotonin at peripheral GI receptors and centrally at the chemoreceptor trigger zone, effectively reducing nausea and vomiting within 1–2 hours after dosing :contentReference[oaicite:3]{index=3}.

🎯 2. Indications in 2025

• Cats: Severe or persistent vomiting (e.g., CKD, chemotherapy, pancreatitis) :contentReference[oaicite:4]{index=4}.
• Dogs: Chemotherapy-induced nausea, parvovirus enteritis, vestibular disease, perioperative vomiting, motion sickness :contentReference[oaicite:5]{index=5}.
• Premedication: Used to reduce anesthetic-related nausea :contentReference[oaicite:6]{index=6}.

💊 3. Dosing Guidelines

• Dogs (oral/SC/IV): 0.1–0.5 mg/kg every 8–24 h; in oncology settings, up to 0.5–1 mg/kg TID :contentReference[oaicite:7]{index=7}.
• Cats (oral/SC/IV): ~0.1–0.22 mg/kg every 8–12 h; oncology doses may go up to 0.5 mg/kg :contentReference[oaicite:8]{index=8}.
• Oral tablets, ODTs, and liquids are well absorbed; injectable forms are ideal in hospital settings :contentReference[oaicite:9]{index=9}.
• Can be given with or without food—if GI upset occurs, administer with meals :contentReference[oaicite:10]{index=10}.
• If a dose is missed, give when you remember unless it’s nearly time for the next dose—do **not** double-dose :contentReference[oaicite:11]{index=11}.

⏱️ 4. Onset & Duration

Onset is quick—about 1–2 hours, with effects lasting up to 24 hours :contentReference[oaicite:12]{index=12}.

⚠️ 5. Side Effects & Serious Risks

• Common: constipation, mild sedation, head shaking :contentReference[oaicite:13]{index=13}.
• Less common: diarrhea, arrhythmias, hypotension—monitor at-risk patients :contentReference[oaicite:14]{index=14}.
• Extrapyramidal signs (e.g., abnormal movements) are rare :contentReference[oaicite:15]{index=15}.

🚫 6. Contraindications

• Avoid in pets known to be allergic or hypersensitive to ondansetron or other 5-HT₃ antagonists :contentReference[oaicite:16]{index=16}.
• Use with caution in dogs with MDR1 gene mutation, liver dysfunction, or heart rhythm disorders :contentReference[oaicite:17]{index=17}.

📋 7. Drug Interactions

Interactions include QT-prolonging drugs, serotonergic agents, and apomorphine; inform your vet of all current medications :contentReference[oaicite:18]{index=18}.

📈 8. Monitoring & Follow-Up

• Track vomiting frequency, appetite, energy, stool consistency, behavior daily.
• Monitor blood pressure/ECG in cardiac patients; adjust dose in hepatic disease.
• In oncology or chronic use, reassess nausea triggers and antiemetic effectiveness regularly.

📝 9. Client Education & Home Care

• Explain why ondansetron was chosen and expected benefits (1–2 h relief).
• Demonstrate proper oral or injectable administration.
• Discuss signs of side effects and stress not to double-dose.
• Use Ask A Vet app for reminder alerts, symptom logs, and instant vet connection 😊.

📌 10. 2025 Vet Takeaways

• Ondansetron is a rapid, effective antiemetic for severe nausea and vomiting in dogs and cats.
• Dosing varies by species and condition; injectable routes are useful in hospital settings.
• Generally safe, but watch for GI, neurologic, or cardiovascular side effects.
• Caution with liver disease, MDR1 mutation, and QT-prolonging medications.
• Clear owner instructions and digital support via Ask A Vet enhance safe and effective use 😊.

At Ask A Vet, we empower pet parents with dosing calculators, symptom trackers, side-effect alerts, and 24/7 veterinary guidance to make ondansetron use safe, effective, and stress-free ❤️