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My dog has epilepsy. Is phenobarbital sedation normal at this dose?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Large (61lb +) | Male | neutered | 73 lbs

My dog is 33kg (73lbs). He has known epilepsy. Previously he was prescribed phenobarbital 30mg twice a day and was well controlled on this. He has had increased in frequency in seizure activity, so a new vet prescribed him 90 mg twice a day. Since starting the new dose he has been extremely sedated to the point he cant barely stand. He has been on the new dose for 5 days. I feel that this dose is unsafe and wanted a second opinion on it. What is the normal dosing range for phenobarb for dogs?

2 Answers

Most Helpful Answer

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Answered By Dr. Strydom, DVM

Veterinarian

Published on December 4th, 2019

Phenobarbital therapy in dogs is begun at 2 to 4 mg/kg twice daily. So for a 33kg dog that would mean 66 to 132 mg twice a day. We always try to start low and increase if needed but he was essentially really underdosed in the beginning with taking 30mg twice a day. He is now on a more appropriate dose. Sedation is normal when therapy is initiated but once the dog's body gets used to the drug (after about 2 weeks) he should become more like himself. If you are really worried, you can ask the vet to run a phenobarbital level blood test to see if his dosing is too high and it can be adjusted accordingly. Please be aware that dogs will never be completely seizure free even while on anti-seizure medication. Breakthrough seizures are common but they should be pretty infrequent. If he continues to seizure or does not do well on the phenobarbital there are other medication options so please work closely with your vet.

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    Answered By Vanessa Yeager DVM MPH

    Veterinarian

    Published on November 3rd, 2017

    Hi there and thanks for posting on Petco Pet Education Center, formerly Petcoach. Yes, there is a blood test to check Max's level of phenobarbital. Often times, the phenobarbital level test does include kidney and liver values as well. Every veterinary hospital is going to have a slightly different name for the test, but it is typically called a phenobarbital monitoring panel. Unfortunately, I cannot legally advise on dosing of medication over the internet. All dosage changes to medications should be done with your primary care veterinarian. I hope this helps and best wishes to you and Max.

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