IPODATE TREATMENT OF HYPERTHYROIDISM IN CATS

Objective-To evaluate the efficacy and safety of ipodate in the treatm ent of hyperthyroidism in cats. Design-Prospective case series. Animal s-12 cats with hyperthyroidism treated at The Animal Medical Center be tween November 1994 and March 1996. Procedure-Each cat initially recei ved 100 mg of ipodate/d, PO. The drug's effects on clinical signs, bod y weight, heart rate, and serum triiodothyronine (T-3) and thyroxine c oncentrations were evaluated 2, 4, 6, 10, and 14 weeks after initiatio n of treatment. A CBC and serum biochemical analyses were performed at each evaluation to monitor potential adverse effects of the drug. Dos age of ipodate was increased to 150 mg/d and then to 200 mg/d at 2-wee k intervals if a good clinical response was not observed. Results-8 ca ts responded to treatment and 4 did not. Among cats that responded, me an body weight increased and mean heart rate and serum T, concentratio n decreased during the study period. Among cats that did not respond, mean body weight decreased and mean heart rate and serum T concentrati on were not significantly changed. Serum thy roxine concentration rema ined high in all cats. Adverse clinical signs or hematologic abnormali ties attributable to ipodate treatment were not reported in any of the cats. Clinical Implications-Ipodate may be a feasible alternative to methimazole for medical treatment of hyperthyroidism in cars, particul arly those that cannot tolerate methimazole and are not candidates for surgery or radiotherapy. Cats with severe hyperthyroidism are less li kely to respond to ipodate than are cats with mild or moderate disease , and cats in which serum T, concentration does not return to the refe rence range are unlikely to have an adequate improvement in clinical s igns.