Phenobarbital

Introduction

Phenobarbital is an anticonvulsant medication aimed at reducing the frequency and severity of your pet’s seizures. While it is unlikely to completely eliminate seizures, the goal is to make them less frequent and less severe.

Skeletal formula of Phenobarbital

Missed doses and Changing medications

Consistent administration of Phenobarbital is crucial. Set reminders to give the medication on schedule, which is typically twice a day, with or without food. If a dose is missed, administer it as soon as possible, even if it coincides with the next scheduled dose, as stopping suddenly can provoke seizures. Always consult with your veterinary team before making any changes to your pet's medication regimen, especially with seizure medications, which should generally be tapered rather than stopped abruptly.

Monitoring and Lab work

Regular veterinary visits are necessary when your pet is on Phenobarbital, with a minimum recommendation of twice yearly to comply with prescription regulations for controlled substances. Initial testing will include liver function tests to ensure the medication's suitability for your pet.

Monitoring Phenobarbital levels is crucial two weeks after starting the medication or changing the dose and every six months thereafter. General blood work and liver tests are recommended annually. The bile acids test requires fasting and a two-hour clinic stay; consult us beforehand if this overlaps with your pet's medication schedule.

Potential Side effects

Many pets will take this medication with no side effects, or a low level of tolerable side effects. Regular checkups and bloodwork ensure that we are using this very effective seizure medication safely. You should contact your medical team if any side effect is excessive and interfering with you or your pet’s quality of life:

Many pets will act sleepy or drunk while their body adjusts to the medication. It can take two weeks for some pets to adjust. If your pet is especially uncoordinated, keep them away from things like swimming pools and staircases until they are more sure on their feet.
Some pets will be thirsty and will need to urinate more often on this medication. It is important not to restrict their water intake during the day. If they are having accidents overnight, you may pull up their water after dinner time, but be sure to give them a full bowl of water in the morning.
Some pets will be much hungrier on this medication. Monitor the amount of food they are eating. It may be helpful to switch them to a diet food so they can eat more food and not get fat. It is also important to watch for inappropriate eating, some dogs will start eating toys or getting into the garbage while they are on this medication.
Taking this medication will interfere with common test for thyroid function in dogs. It does not seem to cause hypothyroidism, rather it only changes the results on the blood test. If you believe your pet has a thyroid condition that requires monitoring, discuss this with your veterinarian before starting this medication.
This medication will likely cause an increase in your pet's liver enzymes and rarely can cause liver dysfunction. An increase in enzymes alone does not mean your pet has a liver problem. Other test (like a bile acids test) are helpful in making sure that liver changes on blood work are just the expected changes and not a liver problem.
Rarely, this medication can cause changes in your pet’s red and white blood cells, called blood dyscrasias. This can be dangerous, but stopping the medication usually reverses this effect.
Uncommonly this medication can contribute to developing a condition called pancreatitis. If your pet has chronic pancreatitis, or starts vomiting after starting this drug, please contact the medical team.
Rarely phenobarbital use has been associated with itching or other skin lesions. If you notice an increase in redness or itching or if your pet develops sores, contact the medical team.