Clinical Information
Use as directed by your veterinarian. Shake well before each use. If you miss a dose, give it as soon as you remember unless it is close to the next scheduled dose. Do not give two doses at the same time. Your veterinarian will decide how long your pet needs treatment.
Phenobarbital raises the level of a calming chemical in the brain called GABA. This chemical slows down overactive nerve signals that can trigger seizures. Most pets start to show fewer seizures within 1-2 weeks, but full control may take up to 4 weeks. Each dose lasts about 12 hours in most dogs and 8-12 hours in most cats, so regular dosing is important.
Do not use if your pet is allergic to phenobarbital or other barbiturates (can cause severe reactions). Do not use in pets with serious liver disease because the drug is processed by the liver. Avoid in pets with severe kidney disease or breathing problems, as it may worsen these conditions. Use caution in pregnant or nursing animals; the drug can cross the placenta and enter milk. Pets with a history of porphyria (a rare blood disorder) should not take this medication.
Phenobarbital can interact with many medicines. It may make sedatives (such as benzodiazepines), opioids, or some antihistamines cause extra drowsiness. It can lower the effectiveness of certain antibiotics (like doxycycline) and heart drugs (such as digoxin). It may speed up the breakdown of steroids, birth-control drugs used in breeding programs, and some thyroid medicines. Tell your veterinarian about all drugs, supplements, and herbal products your pet takes. Limit alcohol exposure in pets (for example, dogs given beer by owners) because it increases side effects.
Very common (more than 1 in 10 pets): sleepiness, wobbliness when walking, increased thirst and urination, bigger appetite, and weight gain. Common (1-10 in 100 pets): mild behavior changes such as restlessness or irritability, mild liver enzyme increases seen on blood tests. Uncommon (1-10 in 1,000 pets): severe itching or skin rash, anemia, or low white blood cell count. Rare but serious: liver failure (yellow gums, vomiting, loss of appetite), severe allergic reaction (facial swelling, trouble breathing). Most mild side effects improve after the first 2-3 weeks, but contact your veterinarian if they are severe or persistent.
Store at room temperature (68-77°F, 20-25°C) in the original tightly closed bottle. Protect from excess heat, cold, and direct sunlight. Do not freeze. Shake well before each dose to ensure even mixing. Keep out of reach of children and animals. Discard any leftover suspension 6 months after opening or on the expiration date, whichever comes first. Return unused medication to a veterinary pharmacy take-back program when possible.
Frequently Asked Questions
Q:How do I give this suspension to my pet?
A:Use the oral syringe provided to measure the exact dose. Gently insert the syringe into the side of your pet’s mouth and slowly squirt the medicine so they can swallow without choking. Giving it with a small treat or meal may help reduce stomach upset.
Q:When will I see fewer seizures?
A:Many pets start having fewer seizures within 1–2 weeks, but it can take up to a month to see full benefit. Keep a seizure diary to track progress and share it with your veterinarian at follow-up visits.
Q:What should I do if my pet seems very sleepy?
A:Mild sleepiness is common during the first few weeks and often improves. If your pet is too drowsy to eat, walk, or play, call your veterinarian. The dose may need adjusting.
Q:Is blood testing really necessary?
A:Yes. Phenobarbital can affect the liver and blood counts. Regular blood tests help your veterinarian make sure the drug level is in the right range and that your pet’s liver is healthy.
Q:Can I stop the medication once seizures are gone?
A:Do not stop suddenly. Stopping phenobarbital too fast can trigger severe, life-threatening seizures. Your veterinarian will decide if or when it is safe to taper the dose.
Q:What if I spill or miss a dose?
A:If you spill a dose, simply give the next scheduled dose as normal. If you miss a dose, give it as soon as you remember unless it is close to the next one. Never double up doses without veterinary advice.
Q:Does phenobarbital affect vaccines or other treatments?
A:It usually doesn’t affect routine vaccines, but it can speed up the breakdown of some medicines. Always remind your vet that your pet takes phenobarbital before new treatments are started.