Safety Concerns for transdermal thiamazole

RE: Safety Concerns for transdermal thiamazole

Kate Richardson — Fri, 20 Nov 2020 11:12:20 GMT

I rarely use it for the same concerns above, but when I have done, it works.

RE: Safety Concerns for transdermal thiamazole

Bob Russell — Fri, 20 Nov 2020 11:09:22 GMT

I have never used the transdermal products and the EMA report does highlight some real issues. I cannot see why it should be used in any but the most extreme situations.

Nice idea but really only suitable for single cat households where the cat is extremely uncooperative, the cat does not tolerate stroking and there are no children about.

Fair enough to have the product available but the vet has to do some really careful thinking before prescribing. Euthanasia could be the most appropriate alternative in some cases.

RE: Safety Concerns for transdermal thiamazole

Thomas Johnson — Fri, 20 Nov 2020 08:33:49 GMT

[quote userid="9515" url="~/001/veterinary-clinical/small-animal/f/misc-clinical-discussions/29498/safety-concerns-for-transdermal-thiamazole/226884#226884"]True, but a European application to market a transdermal thiamazole solution for cats was withdrawn in 2014 because the regulatory assessors indicated that the product would not be approved due to the negative risk-benefit ratio. As well as doubts about the efficacy of the product, studies showed that thiamazole residues remained at the application site for several days and this gave the assessors cause for concern about the safety of the product to users. You can read it here: www.ema.europa.eu/.../withdrawal-assessment-report-enthryv_en.pdf[/quote]

Thank you for sharing that, my big concern with it, and the reason I use it very infrequently, has been the risk of human exposure. The warnings on the oral products, do not crush tablets, liquid must be given straight in to mouth, had always made me very uneasy about owners smearing it on cats' ears, as even if it was reasonably well absorbed it would inevitably lead to some environmental contamination.

RE: Safety Concerns for transdermal thiamazole

Sarah Keir — Thu, 19 Nov 2020 19:38:00 GMT

True, but a European application to market a transdermal thiamazole solution for cats was withdrawn in 2014 because the regulatory assessors indicated that the product would not be approved due to the negative risk-benefit ratio. As well as doubts about the efficacy of the product, studies showed that thiamazole residues remained at the application site for several days and this gave the assessors cause for concern about the safety of the product to users. You can read it here: www.ema.europa.eu/.../withdrawal-assessment-report-enthryv_en.pdf

RE: Safety Concerns for transdermal thiamazole

Thomas Johnson — Thu, 19 Nov 2020 17:57:09 GMT

[quote userid="9515" url="~/001/veterinary-clinical/small-animal/f/misc-clinical-discussions/29498/safety-concerns-for-transdermal-thiamazole/226783#226783"]I thought I was imaging this study! I remember it was mentioned on a CPD course a few years ago but I have been unable to track down anything about it. Do you have any information?[/quote]

I'm not a big fan of the transdermal gel, for the same reasons that others have given, but I'm very sceptical about this study. If the fluorescent dye isn't absorbed through the skin it's inevitably going to end up spread further over the cat and the house, but that doesn't mean that the same thing happens to the methimazole, it may be absorbed and less of it is then spread elsewhere.

RE: Safety Concerns for transdermal thiamazole

Sarah Keir — Tue, 17 Nov 2020 18:01:26 GMT

Hi Bob,

I thought I was imaging this study! I remember it was mentioned on a CPD course a few years ago but I have been unable to track down anything about it. Do you have any information?

RE: Safety Concerns for transdermal thiamazole

Bob Russell — Tue, 17 Nov 2020 17:20:32 GMT

I seem to remember someone added a fluorescent dye to the gel. Apparently it was quite a shock to find out just where this stuff landed.

I just cannot see why it would be needed except in the most extreme circumstances. Nor can I see why people would take the risk.

The new Thiamacare is is half the volume so should be easier still.

RE: Safety Concerns for transdermal thiamazole

bob lehner — Mon, 16 Nov 2020 10:49:26 GMT

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/f/misc-clinical-discussions/29498/safety-concerns-for-transdermal-thiamazole/226703#226703"]Had new vet last week ask me if we had any. I'm all for clinical freedom and said whilst I hadn't ever used it I'm sure could get some. Had a rummage on the shelf and found a tube that expired in 2018. I explained that it needed ordered for individual patient as I understood it, but so long as he had someone would pay for it and wished to use it shouldn't be a problem. I looked on the back of the 2018-expired tube to find my name - apparently I'd ordered it![/quote]

I think quite a number of vets are either unaware, or forget, that so-called 'specials' (increasingly popular) are not authorized medicines and as the article points out lie at the bottom of the cascade - i.e. come after other authorized veterinary medicines, human medicines and authorised imports. They cannot be used as a first choice without first exploring and eliminating the other possiblities.

I was rather bemused when my son's cat was recently diagnosed as hyperthyroid and then prescribed the transdermal product without any other licensed options being tried. As the cat spends about 90% of its time asleep on the matrimonial bed, which is also frequented by two small children, I was a bit concerned re the potential environmental contamination risks.

RE: Safety Concerns for transdermal thiamazole

David Mills — Sun, 15 Nov 2020 22:34:50 GMT

I can't see why anyone would still use it. There was a study I think that showed most of it was ingested anyway - however it was spread over a lot of the coat first which has to be a concern. I suppose just squirting thyronorm on the cat would work in the same way.

RE: Safety Concerns for transdermal thiamazole

Beats — Sun, 15 Nov 2020 19:58:03 GMT

Interesting!

Had new vet last week ask me if we had any. I'm all for clinical freedom and said whilst I hadn't ever used it I'm sure could get some. Had a rummage on the shelf and found a tube that expired in 2018. I explained that it needed ordered for individual patient as I understood it, but so long as he had someone would pay for it and wished to use it shouldn't be a problem. I looked on the back of the 2018-expired tube to find my name - apparently I'd ordered it!

RE: Safety Concerns for transdermal thiamazole

Busybee — Sun, 15 Nov 2020 19:34:12 GMT

I've used it very successfully on one case (so only n=1). A very aggressive cat with elderly but capable owners and the only way they could medicate the cat was the transdermal thiamizole; we tried all the other options first. We went through all the possible risks and expectations and the cat, and owners, did incredibly well for a number of years. Guess it comes down to careful case and client selection, providing written instructions, getting signed consent and documenting everything.

I have hypothyroidism myself so have always been very careful handling any thyroid meds!

RE: Safety Concerns for transdermal thiamazole

Sarah Keir — Sun, 15 Nov 2020 16:20:28 GMT

That's good to hear. Perhaps the practices I have worked in aren't so current.

RE: Safety Concerns for transdermal thiamazole

KathW — Sun, 15 Nov 2020 15:56:59 GMT

Haven't used it for many years now. With thyronorm available compliance has become less of an issue for some clients/cats. Whenever I did prescribe it I ensured the owners were aware it was a non licensed product being prescribed under the cascade and I always discussed its use and gave them relevant information sheets on its use and possible side effects etc.