Mirtazapine (Remeron) for Pets in 2025 🐾

Mirtazapine has become an essential tool in veterinary medicine—not for treating depression, as in humans, but for addressing appetite loss and nausea in pets. I’m Dr Duncan Houston BVSc, and this 2025 guide explores how Mirtazapine works, its forms, safety, and how to avoid serotonin syndrome in dogs and cats 🐶🐱

🍽️ What Is Mirtazapine?

Mirtazapine is a tetracyclic antidepressant used in veterinary medicine primarily for:

• 🍽️ Stimulating appetite
• 🤢 Controlling nausea
• 😿 Supporting pets with chronic illness, cancer, or undergoing chemotherapy

💊 Available Forms

• 💊 Tablets: 7.5 mg, 15 mg, 30 mg, 45 mg
• 🧴 Transdermal gel (Mirataz®) for cats—applied to the inner ear

📋 How Mirtazapine Is Used in Pets

🐶 Dogs (oral tablets):

• Typically given once daily
• If ineffective, consider alternatives like capromorelin or cyproheptadine

🐱 Cats (tablet or transdermal gel):

• Tablets: every 1–3 days, but often hard to split safely
• Transdermal gel (Mirataz): applied to ear daily, alternating ears daily
• Wear gloves & avoid pet contact for 2 hours post-application

⚠️ Cats with Kidney/Liver Disease:

Lower dose or reduced frequency is recommended due to slower drug clearance. Consult your vet for adjusted protocols.

🧠 How It Works

Mirtazapine increases norepinephrine and serotonin levels in the brain, which helps improve mood and appetite. In the GI tract, it has the opposite effect on serotonin—blocking it to reduce nausea and vomiting.

⚠️ Side Effects

• 💤 Drowsiness (most common)
• 🐾 Increased affection or vocalization (cats)
• 🚨 Hyperactivity in ~11% of cats (especially with transdermal gel)
• 📈 Increased heart rate or blood pressure (higher doses)
• 🔬 Rare bone marrow changes—monitor in pets with blood disorders

💥 Serotonin Syndrome: Know the Signs

Occurs if Mirtazapine is combined with other serotonin-enhancing drugs. Symptoms include:

• ⚡ Tremors, twitching, shivering
• 🐾 Agitation or pacing
• 😵 Dilated pupils, disorientation
• 🌡️ High fever or blood pressure
• 😰 Breathing difficulty

Cyproheptadine may be used as an antidote if serotonin syndrome occurs. Contact your vet immediately if symptoms are seen.

🚫 Drug Interactions

• ❌ SSRIs (e.g., fluoxetine)
• ❌ MAO inhibitors (e.g., selegiline, amitraz)
• ❌ Tramadol
• ❌ Buspirone, metoclopramide, erythromycin, ketoconazole, cimetidine
• ⚠️ Allow at least 14 days between using mirtazapine and any MAO inhibitors

🧪 Monitoring & Precautions

• 🔍 Monitor bloodwork in pets with liver or blood conditions
• ⏳ Adjust frequency for pets with kidney or liver disease
• 👶 Not approved for pets under 2 kg or younger than 6 months (gel form)
• 🚫 Not studied for use in pregnancy or lactation

📲 Ask a Vet for Tailored Advice

If you're unsure whether mirtazapine is right for your pet, or you’re noticing unusual behavior, download the Ask A Vet app for immediate help from licensed veterinary professionals 🐾💬

✅ Summary

• ✔️ Appetite stimulator & anti-nausea med for dogs & cats
• ✔️ Tablet & transdermal gel forms available
• ⚠️ Monitor for drowsiness or hyperactivity
• ⚠️ Avoid drug interactions that can lead to serotonin syndrome
• ✔️ Consult your vet for kidney/liver disease dosing or other conditions

Whether recovering from illness, undergoing chemo, or living with chronic disease, pets with poor appetite or nausea can benefit greatly from mirtazapine—when used carefully and monitored closely 💛

Questions about dosing, side effects, or alternatives? Use the Ask A Vet app to speak directly with experts who care 🩺🐾

— Dr Duncan Houston BVSc