My 16 y/o male cat was diagnosed with hyperthyroidism and prescribed felimazole 2.5mg twice a day-quickly put weight back on and responded well over about ten days.i noticed he had a twitch which increased to jerks over several days from about 1 1/2 hours after his first tablet.informed the vet but they didn't see a connection.told to take him off it for a couple of days-then to restart,with the thinking that if the jerks/twitches stopped and then restarted when meds recommenced, was meds.just before the two days were over my cat then had a seizure which he had never had before.kept off meds for about a week then put back on by original vet who said had never heard as a reaction.cat had slight twitches but virtually stopped-as soon as he went back on the felimazole tablets he started twitching and jerking again-again my vet said to keep him on the medication.again I took him off the meds after ten days-within three days he had another seizure.both at night in his sleep(the one time previously he had not really twitched on the meds), both when taken off the meds.since being off the meds and having the seizure the twitches and jerks had stopped.he has now been off the felimazole for ten days and needs treatment.i have started him on y/d food-hills-and was told by the emergency vet he saw after the second seizure that he shouldn't be on felimazole as there was a bit of a coincidence this had occurred again-so probably a link,also that my vet needed to refer back to manufacturer on this.now-i have seen my vet today to look at treatment options and he has suggested the transdermal gel-0.1ml/twice day.my concern is that this is the same medication and will have the same impact-ie seizure.my vet again doesn't seem too concerned and has also suggested surgery-but obviously not until my cat's heart rate is lowered.I wonder if you might be able to advise if this gel is likely to have the same reaction as the Felimazole tablets please?my vet suggested that the likelihood was a reaction to something in the tablet-but as they appear to contain justthiamazole(methiamazole)2.5mg as active substance with excipients titanium dioxide and erythrosine could these ingredients have caused the seizures?-doesn't seem likely but I'm not the vet.

My cat Courage has been taking methimazole for seven months. He has gained weight and seems much better. However, his face swells every few days for about twenty minutes and he has to keep his mouth open to breath. I have read that this can be a symptom of an allergy to methimazole, but he had this "face swelling" before he ever took methimazole. Can it be a symptom of hyperthyroidism? I have kept a food diary to see if there is a cause that I can find, but it seems entirely without a pattern. In fact, the swelling seems to disappear quicker if I give him food. I bought him an air purifier and I run it day and night, but it doesn't make a difference. He gets the swelling in the winter when the windows are closed and in the summer when the windows are open (we live in Minnesota where the winters are very cold and snowy and the summers are very hot and humid) I was wondering if it is an allergy and might respond to Zyrtec. Is that safe for cats with hyperthyroidism? Or should I ask my vet for hydroxyzine? Is there any allergy medication that is preferred?

My cat had an allergic reaction to the thyroid meds (itchy, facial swelling, lethargy) so we took her off the meds. It's been 1 week and she's doing a lot of vomiting and is still very lethargic. How long would it usually take before they are back to themselves?

My cat started methimazole about 3 weeks are and yesterday she started keeping her ears down and she seems sleepy all of the time. Are these serious side effects from methimazole? Should I discontinue her methimazole?