Potassium bromide levels

Re: Potassium bromide levels

ilanit — Mon, 28 May 2012 17:53:52 GMT

[quote user="Mark Lowrie"]

I wouldn’t be too concerned (yet) about hepatic problems from phenobarbitone given the signs the dog is showing. I would agree with Andrew and repeat the bile acid stimulation test in one or two weeks as we should not ignore it. You mention the rest of the bloods are fine so, provided this has included urea, glucose, cholesterol and albumin again, I would take a more relaxed approach and not rush into discontinuing the phenobarb as I think this would cause the dog more problems. Also, phenobarb can be stopped fairly quickly if necessary although there is no data to suggest the best way to do this – I decide based on a case by case basis of how quickly we need to get the dog off the meds.

The seizure frequency does not sound too severe either. Therefore I wouldn’t rush into using Keppra. But, if the repeated bile acids do suggest problems, tapering phenobarb and starting Keppra is fine (Keppra takes very little time to reach effective concentrations – less than 48 hours). The reason I am hesitant with starting Keppra + KBr is the cost but also (in my opinion) the long-term efficacy just doesn’t seem as good as PB + KBr.

[/quote]

Thanks for you advise

Re: Potassium bromide levels

Mark Lowrie — Mon, 28 May 2012 16:46:34 GMT

[quote user="Hannah Bose"]

Can I piggy back on the back of this to ask general questions about phenobarbitone monitoring?

Idexx say to sample 12 hours post-pill when on BID dosing, but for peak values, where toxicity is suspected, sample 5 hours post-pill.

I would have thought that if I have a dog on phenobarbitone the purpose of the blood test is to determine if the level is too high/whether I can increase it any more. Therefore I want to know the peak values ie the 5 hours post-pill.

The nadir, on the other hand, if it is still within the reference range, does not tell me much. So... why do Idexx make it sound like the 12 hours is the norm?

CTDS recommend 5 hours post-pill as the routine time to test. However, they recommend serum gel tubes whereas Idexx specify separated serum.

Lastly, at uni, I distinctly remember being taught that the time of sampling does not matter that much, but definitely put in a plain serum tube.

[/quote]

Hi Hannah, the approach I always use is to make sure you take the sample at the same time post pill. It doesn’t matter if this is 2 or 10 hours post pill so long as you are consistent. This is based on a recent study:

http://www.ncbi.nlm.nih.gov/pubmed/19897869

They found little difference in the serum concentration of phenobarbitone in peak and trough samples when dogs were given lower doses of phenobarbitone (less than 10 mg/kg/day). At higher doses (i.e. greater than 10 mg/kg/day) there was a significant difference and hence the reason for recommending consistency in your sampling time.

Re: Potassium bromide levels

Mark Lowrie — Mon, 28 May 2012 16:40:59 GMT

Re: Potassium bromide levels

ilanit — Mon, 28 May 2012 16:19:12 GMT

[quote user="Mark Lowrie"]

Hi illanit, just seen your post. Do you have any idea of the current seizure frequency? Also, is the dog showing any side-effects from phenobarb or KBr?

I would agree we tend to look at the blood concentrations rather than the dose for KBr and PB. Are you certain the owner is giving this high dose and hasn’t got confused. Non-compliance would be a common reason for failure/problems with anti-epileptic drugs.

Re: levetiracetam – the way I would use it depends on the current seizure frequency.

[/quote]

The dog apparently was having more frequent seizures and longer ones maybe 6 months ago. That's when owner decided on own account to increase KBR dose. The last 3 months he didn't have any seizures apart from 2 short ones in the last 2 weeks.

Otherwise dog is doing fine apart from 2 weeks ago when dog was lethargic, polyuric, retching and drooling for 24 hours. But after 24 hours hospitalisation/drip dog was fine (bloods were normal apart from increased liver enzymes). That's when I saw him for the first time and decided to measure levels.

He's not showing any signs of liver failure, but I do not like the BA results and do not want to wait to see how bad it gets before doing something. After all weaning off PB takes ages anyway. Wouldn't it be better to change from PB to Levetiracetam in conjunction with KBR to get risk of the hepatotoxic drug altogether?

Re: Potassium bromide levels

HMC — Mon, 28 May 2012 14:49:10 GMT

Can I piggy back on the back of this to ask general questions about phenobarbitone monitoring?

Idexx say to sample 12 hours post-pill when on BID dosing, but for peak values, where toxicity is suspected, sample 5 hours post-pill.

The nadir, on the other hand, if it is still within the reference range, does not tell me much. So... why do Idexx make it sound like the 12 hours is the norm?

CTDS recommend 5 hours post-pill as the routine time to test. However, they recommend serum gel tubes whereas Idexx specify separated serum.

Lastly, at uni, I distinctly remember being taught that the time of sampling does not matter that much, but definitely put in a plain serum tube.

Re: Potassium bromide levels

Mark Lowrie — Mon, 28 May 2012 09:25:30 GMT

Hi illanit, just seen your post. Do you have any idea of the current seizure frequency? Also, is the dog showing any side-effects from phenobarb or KBr?

Re: levetiracetam – the way I would use it depends on the current seizure frequency.

Re: Potassium bromide levels

ilanit — Mon, 28 May 2012 06:15:48 GMT

Thanks! I will do just that. (learned my lesson about gel tubes )

If I would change to levetiracetam, how would you use it? As an add on therapy with KBR after taking off PB? Or as monotherapy?

Re: Potassium bromide levels

Rob Loxley — Sat, 26 May 2012 08:47:44 GMT

[quote user="ilanit"]Was surprised to see that the actual potassium bromide levels are below therapeutic range with such a high dose.[/quote]

Also dietary salt intake will have an effect on the bromide level

Re: Potassium bromide levels

Andrew Kent — Fri, 25 May 2012 22:04:56 GMT

There is big variation in dose requirements of KBr, having said that if you took the sample in a gel tube (even if removed) I would not trust it and would repeat using a plain tube. I regard 20 as the minimum therapeutic dose for phenobarbitone so do not see that you have any scope to reduce this without seizures. The bile acid stim is worrying and I would not ignore it, I would repeat it in a few weeks and if significant changes are consistent then consider alternative medications (eg levetiracetam) Andy

Re: Potassium bromide levels

Michael Woodhouse — Fri, 25 May 2012 20:42:04 GMT

[quote user="ilanit"]Or should I not worry too much since the dog is doing fine and check levels again in couple of months? [/quote]

That's what I'd do. Treat the dog not the numbers