Tapazole for Felines

Vets commonly prescribe Tapazole (methimazole) for the treatment of hyperthyroidism, or overactive thyroid gland, in cats. Although most frequently used as part of a long-term disease management program, short-term use of Tapazole also reduces the levels of thyroxine in the blood to make the cat a better candidate for corrective surgery.

  1. How It Works

    • Tapazole easily absorbs into the bloodstream from the gastrointestinal tract after oral administration. It works directly on the thyroid gland to inhibit the production of thyroxine without interfering with supplemental thyroid hormone medication. Cat owners usually give the pill two to three times daily with food to minimize nausea, and twice-yearly thyroid tests are necessary to adjust the dose to the lowest effective concentration.

    Advantages

    • An inexpensive, effective medication that most cats tolerate well, Tapazole is safe and gentle enough for long-term use, which often results in remission of the disease. Administering the pill with food helps eliminate the most common side effects.

    Disadvantages

    • Pregnant or nursing cats are not candidates for Tapazole treatment because the drug is excreted in milk. Long-term use sometimes causes liver damage, so the cat's liver function should be monitored periodically. In rare cases, an unfavorable reaction to Tapazole produces vomiting and loss of appetite, which you should report to your vet. Giving the pill with a small amount of food masks the bitter taste and reduces the chance of vomiting.

    Supplemental Treatment

    • Because excess thyroxine levels in the blood actually benefit the kidneys by allowing them to filter waste more efficiently, support for kidney function should accompany any medication that lowers these levels. Prescription kidney diets are formulated to produce less waste, and supplementation with B-complex vitamins and vitamin C also help increase kidney function.

    Alternatives

    • Surgery to remove the diseased portion of the thyroid gland is the most effective treatment for hyperthyroidism, but not all cats are candidates for surgery. Radiation therapy is also effective and does not require anesthesia, but it is expensive and not available in all areas. Cats with low kidney function generally do not do well following surgery or radiation therapy, and long-term Tapazole therapy generally serves them best. Some pharmacies compound a topical form of Tapazole, but many vets consider it less effective than the oral medication.