Phenobarbital & the Liver

Question
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Followup To
Question -
I know you've listed your expertise as dermatology and ear diseases of dogs and cats, but I'm hoping that you will be able to answer my question with a little more expertise than the other "experts", since you are a doctor.

One morning about 3 or 4 years ago my Cairn terrier had a couple of mild seizures, and one seizure which was more severe that lasted about 30 seconds (he actually lost his balance and fell over). I immediately took him to my vet, and he was put on both phenobarbital and valium. After a short period of time, that was changed to only phenobarbital (one half grain 2X daily). He's had no seizures, (that I've noticed) to date, and he's always been getting the same dosage phenobarbital. The dog is now 9 years old.

Just the other day at his yearly vet exam, I asked about slowly weaning the dog off the phenobarbital, because I know of it's effects on the body. The vet agreed, given the fact the dog has been seizure free for at least 3 years. I'm now giving 3/4 of the half grain tablets 2X a day, and sometime in November with my vet's approval I'll take that down to 1/4 grain 2X a day.

At this same exam, I also had the doctor do blood tests to see how the phenobarbital is effecting my dog's liver.

I just spoke to my vet, who told me that the liver values are elevated, at around 700 (I don't have the paper work, and that's how it was described). My vet said normal liver values are around 100. It is suspected that the phenobarbital has caused the elevated liver values, since the dog has no obvious symptoms of liver disease. My dog has a great appetite, normal bowel and urine function and seems quite happy. He's as active as any 9 year old dog.

My question is, over time will the elevated liver values drop off to normal levels as the phenobarbital is slowly decreased or might this be start of potentially life threatening or chronic health concerns?

Thank you in advance for your help,

Patti

Answer -
I would just take the dog off of the phenobarbital.  You do not need to wean him off. Then recheck the ALT levels in a month.




Hi Dr.

Thank you for your response, I realize that skin and ear problem questions are what you prefer to answer, perhaps seizures are out of your realm of experience.

To be honest, everything I've ever read about using Phenobarbital for seizures, (and the advice I got my vet as well) says that any sudden drop-off in medication can trigger life-threatening seizures. Assuming a dog has been seizure free for at least a year, one must slowly scale back on the amount of Phenobarbital given, over the course of many months (if not a full year)

You might want to read more about it here (though it's all over the Internet):

http://www.marvistavet.com/html/body_seizure_disorder.html

Scroll down to the section entitled: CAN SEIZURE MEDICATION BE STOPPED?


-Patti  

Answer
I have taken dogs off of phenobarbital abruptly when switching to potassium bromide and there has not been any liver or other medical problems associated with phenobarbital withdrawl. I went to that website and I looked at the section where they talk about withdrawl time.  I also checked in several textbooks and the formulary and I could not find anything that would substantiate their statement.  I agree that if you do not know if the dog is actually siezure prone, then slowly withdraw, but there is no medical need to withdraw slowly.