My cat has been on low dose tapazole (.1 per day) transdermal. It did not help her thyroid much. So they increased the dose to .15 per day. After rechecking, her thyroid was wonderful!!!!! BUT her ALT level shot up to 489!!!!!!!!!!!! It had been high since on the low dose tapazole (190), but not as high as it is now. They want me to increase her tapazole, but if her thyroid level is fine, should I really increase the meds? Could her ALT level be high due to reaction to tapazole?
Thank You
Sight unseen, blah blah blah….
But, tapzole (methimazole) CAN actually CAUSE liver changes. So, I am not liking the increase in ALT with the decrease in thyroid. Usually we try to get the T4 into a low end of normal range. If you are still high end, you may not be controlled as much as you would like. But, I would still be concerned about the tapazole. When using this drug, we monitor the T4, obviously, but also the white cell count (it can get too low, which makes the cat more prone to infections), the BUN/CREAT (kidney tests because if the cat has both kidney failure and hyperthyroid disease, we can’t treat the thyroid as aggressively), and ALT (liver-it is extremely common for hyperthyroid cats to have hi ALTs, which should go down with treatment, but also to be sure it isn’t going UP).
Your options are to discuss going off the tapazole and seeing if the ALT goes down, or getting an abdominal ultrasound and liver biopsy to see if the changes are toxic (ie, the tapazole), or other liver disease (with no relation to the drug). The only other drug available is PTU (propylthiouracil), but it is never used anymore because it has even more side effects. You may need to do the radioactive iodine treatment to avoid medication. This is considered the best option with the least side effects (except maybe your pocket book!), and only treats the tumor cells, leaving the normal thyroid cells alone. However, it has to be done in certified/ licensed facilities and they may not be in your area. In that case, you may need to consider surgery. In cats, the thyroid can be in multiple places down the neck and even into the chest, so it can be next to impossible to get all of the thyroid out (this is why it is rarely necessary to give thyroid supplements post-op), and you have to be very careful to not damage the parathyroids that sit right on top of them. But, surgeons are easier to find than radioactive facilities.
Good luck with your kitty. I use a lot of tapazole in my practice, but my own cat couldn’t take it (completely stopped eating, no matter the dose), I see a few allergic cats (tremendous facial itching), one that dropped its white count precipitously and got sick from that, and one that the liver was the problem. So, while there ARE side effects, they are uncommon, but if yours is the unusual one, that doesn’t help much!
Laurie S. Swanson, DVM
Waukegan Pet Clinic
Waukegan, IL
Yes. Also happens due to the disease process itself. Good idea to use liver antioxidant like Denamarin from Nutramax. Also consider the radioactive iodine treatment- i did have it done to personal cat and she is great 2 years later despite the concerns with the radioactivity.
Pam Wood, DVM
VCA Wellington Animal Hospital
Loxahatcheeo, FL
My cat who was being treated for hyperthyroidism with methimazole suddenly became quite ill last week. His white cell count was down to 1000 and according to one blood test hit platelets were (seems radically low so I suspect it might have been an error) was 13,000. BUN, Creatnine, and Bilirubin were all elevated but his ALT was normal. Upon release from the hospital (after IV treatment) there was much improvement but his ALT which was normal was now elevated.
My concern is this. How to proceed. I love this cat very much and do not want to cause him undo suffering. I am concerned about possible side effects of alternative meds and we have ruled out radio active iodine treatments. My goal for him is optimum health, comfort, and humane treatment over simple longevity. One vet recommended against surgery because he was high risk, and another said that if his next blood tests were normal that surgery was an option. I am happy to proceed with surgery if there is some likelihood of a positive outcome. Unfortunately with a different cat of ours he ended up having to be put down 2 months after surgery making the end of his life a misery. I do not want that to be this cat’s fate. Any thoughts are appreciated. Thanks.