Phenobarbital for Pets in 2025 🧠

Phenobarbital remains one of the most trusted and widely used medications for seizure control in dogs and cats. It's effective, affordable, and time-tested. I’m Dr Duncan Houston BVSc, and this 2025 guide explores how phenobarbital is used in pets, what to monitor, and what owners need to know for safe long-term management of epilepsy or seizure disorders 🐶🐱

🔬 What Is Phenobarbital?

Phenobarbital is a barbiturate medication that works by depressing abnormal activity in the brain. It’s used to manage epilepsy and other seizure disorders in dogs and cats—regardless of the cause (epilepsy, tumors, infections, poisoning, etc.).

💊 Available Forms

• Tablets: 15 mg, 16.2 mg, 30 mg, 32.4 mg, 60 mg, 64.8 mg, 97.2 mg, 100 mg
• Liquid: 20 mg/5 mL elixir
• Injectable (hospital use only)
• Compounded transdermal gel or flavored suspensions for cats

📋 How It’s Administered

• 📆 Typically dosed 2–3 times daily (usually twice for convenience)
• 🍽️ Can be given with or without food
• ⏰ Give missed doses when remembered—do not double up
• 🧴 Store at room temperature, away from light

⚠️ Common Side Effects

• 😴 Sedation (usually short-lived)
• 🍽️ Increased appetite
• 💧 Excessive thirst and urination

Most side effects are temporary or manageable with dosage adjustments. If sedation persists beyond 2 weeks, a blood test may be needed.

🚨 Less Common Side Effects

• 🧬 Liver damage in dogs (associated with high blood levels)
• 🩸 Anemia or bone marrow suppression (rare)
• 🐱 Facial itching in cats

🧪 Monitoring & Blood Tests

• 🩺 Check blood levels 2 weeks after starting therapy
• 📈 Recheck 6 weeks after starting, then every 6 months
• 📊 Monitor liver enzymes (ALT, ALP, AST) regularly
• 🧪 Draw samples just before the next dose (“trough level”)

Phenobarbital induces liver enzymes, which can falsely elevate liver tests—even when the liver is healthy.

🔄 Drug Interactions

Phenobarbital can reduce the effectiveness of many drugs due to enzyme induction in the liver. Always inform your vet of all medications and supplements.

• ⬇️ May reduce effects of: prednisone, doxycycline, cyclosporine, theophylline, estrogen, and others
• ⬆️ Effects of phenobarbital increased by: chloramphenicol, sedatives, antihistamines
• ⚠️ Use cautiously with: rifampin, acetaminophen, NSAIDs (increase liver toxicity risk)

🚫 When to Avoid Phenobarbital

• 🐶 Pets with pre-existing liver disease
• 📈 History of liver or brain bleeding
• ⚠️ Pets with adrenal or thyroid disease (affects test interpretation)

⚠️ Key Warnings

• ⛔ Do not stop phenobarbital suddenly—it can trigger severe seizures
• 📉 If side effects occur, your vet may reduce the dose or add a second med (e.g., potassium bromide in dogs)
• 🧪 Potassium bromide is NOT safe for cats

📲 Ask a Vet If...

• 📞 Your pet misses a dose
• ⚠️ Your pet has more than 2 seizures between blood checks
• 📊 You're unsure how to interpret lab results on liver function

Use the Ask A Vet app for real-time support with seizure control plans, medication adjustments, and lab reviews 🧠🐾

✅ Summary

• ✔️ Phenobarbital is the gold-standard for seizure control in dogs and cats
• ✔️ Effective and affordable for long-term use
• ⚠️ Regular blood testing needed to avoid liver toxicity
• ✔️ Safe with proper monitoring and veterinary guidance

With the right support and testing, phenobarbital can give your pet a stable, seizure-free life 💛

— Dr Duncan Houston BVSc