Phenobarbital side effects--how long?

[jtrosen]

My dog (shepherd/husky mix, 73 pounds, 12 years old) began to have grand mal seizures last week. He had two seizures, one on Sunday and one on Monday, at almost exactly the same time in the evening. After the second seizure, the vet put him on phenobarbital (97 mg/2x per day).

He's been on it for five days now and is still pretty out of it. He is extremely lethargic (sleeps most of the day), has coordination problems, and weakness in his hind end. He walks veeery slowly. He's also extremely hungry and thirsty. I've read that all of these are possible phenobarbital side effects. How long do these usually last before the dog gets used to the medication? I'm hoping that these are not signs that something else is wrong, though I am aware of the possibilities.

[tonyb286]

Hi. You are absolutely right, phenobarbital can produce pancreatitis and liver damage. However that is why it is essential to have a blood check undertaken within the first two weeks of starting it, to ensure it falls within the therapeutic level. It is (ordinarily) only too high a dose that produces pancreatitis and liver damage and that can begin to happen after two weeks. Potassium bromide is the usual first choice for dogs with existing liver issues, but phenobarbital is ordinarily the first choice for those that do not have such problems. Initial high doses are often advised to control severe seizures, which makes it the best choice out of two evils, as it were, because it is more important to control the seizures at the outset.

Tony

[bellalunamitzymoona]

I read the posts about liver damage from ph, and to try bromide. My dog is on both. The bromide is great but you have to watch for pancreatitis. Give bromide with food. My dog had pancreatitis after two weeks from to high a dose

[tonyb286]

Hi. Don't worry too much about the initial side effects of phenobarbital. It is normal practice to start all dogs with seizures on a higher end dose of phenobarbital, just to bring the seizures under control. This drug does have a tranquilizing effect, therefore you can expect your dog to become slow, sleepy, lethargic and unresponsive. This WILL pass. You need to be patient. The next task is to get your dog to the vet in 2 weeks time to have the first  blood test, which will determine whether the dose is too high or too low. There is what is known as a "therapeutic level" of phenobarbital (different for every dog) and the only way of determining this is to have a blood test. As the drug take some time to reach a stable level, the first test should be done two weeks after the drug was started. Has your vet made an onward appointment for this test? If not, telephone them and book one.

One month after that first therapeutic level blood test, there should be a further blood test to check the level again. Then further blood tests every month for 3 months - and then every 6 months.

Phenobarbital has a 12 hour effective period. So this is why your dog is on two doses a day. It is important (I am assuming your vet has explained this) that you ensure the dosages are given at the same times each day, because even an hour or two difference can have a detrimental effect. In fact, what it means is that your dog will go the hour or two without any medication influence, which in turn means there will be an increased risk of seizures occurring during this time.

Finally, don't be tempted to miss a dose or give any different amount other than what is prescribed. This is extremely important. If you have concerns about anything while your dog is taking the medication, please raise it with your vet - don't be tempted to amend the regime yourself.

Hope this helps.

Tony

[jjfarmerj]

My 7 year old Golden Retriever has been having seizures for the past three years.  He had one about every 6 months.  His last seizure/epileptic lasted on and off for two hours and continued 5 hours later.  He was listless and couldn't move.  I took him to the vet.  She gave him a 200.00 shot of phenobarbital and he is now home taking two  table twice daily 64.8 mg.  He isn't the same.  It has been three days.  He isn't responsive and lies around unless he needs to go to the bathroom or walk outside.  Is he getting too much of a dosage?

[tonyb286]

Hi Fran.

Yes, very sad indeed. I am very sorry to read your post today.

Tony

[llanca]

Hi again,  and thank you for your comments.    I am not sure how the vet arrived at the Cancer diagnosis.... however,  during the operation they discovered that there were cancer nodes all along the spermatic cord,  so they dug a big further and the poor dog had cancer in other parts...so naturally this dog was pts.
It turns out that he had a tumour on the brain, (unknown until now)  which caused some fitting, which was then treated with phenobarb,  which did control the fitting but the cancer spread elsewhere.....Such a very sad ending.
Thank you again for all your input
Fran