Anticonvulsant Question

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Caveat: I'm a pharmacist with a dog (9y/o corgi) with new-onset seizures who is under regular care of a vet. I am not seeking advice for his care, just curious about differences in human and vet med.

So Bert is being started on phenobarbital for his seizures. In humans, because the half-life is so long we give a loading dose of 15-20mg/kg and then start maintenance dosing.

Why isn't this done in dogs?

Did you ask your veterinarian why he/she did not use a loading dose?

The reason I ask that is because it is up to the veterinarian's judgement whether the individual case warrants the profound side effects that often occur with administration of loading dose amounts of phenobarbital. So the answer is on a case by case basis, and only your vet knows his/her own reasoning.

He basically said "umm, I'm not sure why we don't, but we never have". I see outdated practices in older physicians regularly, and assumed a bit of the same goes on in the veterinary world as well, particularly in the community setting.

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Mine was not given a loading dose either. I can't recall a reason beyond him not thinking it was necessary. So at least it's not just you?

Originally Posted by njac

Caveat: I'm a pharmacist with a dog (9y/o corgi) with new-onset seizures who is under regular care of a vet. I am not seeking advice for his care, just curious about differences in human and vet med.

So Bert is being started on phenobarbital for his seizures. In humans, because the half-life is so long we give a loading dose of 15-20mg/kg and then start maintenance dosing.

Why isn't this done in dogs?

I think it must be based on the individual veterinarians experience as well as the experience with your dog.

My dog WAS given a loading dose of phenobarb here at the Penn Vet hospital when he began having seizures about two months ago. I would imagine that maybe the severity/duration of seizures might have something to do with it?

Originally Posted by GellaBella

I would imagine that maybe the severity/duration of seizures might have something to do with it?

This is the gist that I got from our pharm lectures. The only time we really talked about loading doses with anticonvulsants was in relation to cluster seizures and emergencies where the seizures won't stop.

Thank you! I had a feeling it was to limit side effects, I also imagine most vets aren't comfortable sending home a patient with a complicated initial regimen and/or admitting them just to load.

I was just wondering if there was any big pharmacokinetic reason.

Originally Posted by njac

Thank you! I had a feeling it was to limit side effects, I also imagine most vets aren't comfortable sending home a patient with a complicated initial regimen and/or admitting them just to load.

I was just wondering if there was any big pharmacokinetic reason.

no big reason. But if I do a loading dose, I hospitalize for 24 hrs (or try to). this is what I was taught in school to deal with side effects and to determine if the seizures are controlled.

There are a variety of reasons to load a patient on anti convulsants. My preference is to load in hospital with IV drugs, however I have loaded a patient at home on oral drugs due to cost of hospitalization. So you can do it either way it just depends on the case.