Methimazole treatment of 262 cats with hyperthyroidism.
The efficacy and safety of the antithyroid drug methimazole were evaluated over a 3-year period in 262 cats with hyperthyroidism. In 181 of the cats, methimazole was administered for 7 to 130 days (mean, 27.7 days) as a preoperative preparation for thyroidectomy. The remaining 81 cats were given methimazole for 30 to 1,000 days (mean, 228 days) as sole treatment for the hyperthyroid state. After 2 to 3 weeks of methimazole therapy (10 to 15 mg/d), the mean serum thyroxine (T4) concentration decreased significantly (P less than 0.001) from a pretreatment value of 12.1 micrograms/dl to 2.1 micrograms/dl. The final maintenance dose needed to maintain euthyroidism in the 81 cats that were given methimazole as sole treatment for hyperthyroidism ranged from 2.5 to 20 mg/d (mean, 11.9 mg/d). Clinical side effects developed in 48 (18.3%) cats (usually within the first month of therapy), which included anorexia, vomiting, lethargy, self-induced excoriation of the face and neck, bleeding diathesis, and icterus caused by hepatopathy. Mild hematologic abnormalities developed in 43 (16.4%) cats (usually within the first 2 months of treatment), which included eosinophilia, lymphocytosis, and slight leukopenia. In ten (3.8%) cats, more serious hematologic reactions developed including agranulocytosis and thrombocytopenia (associated with bleeding). These hematologic abnormalities resolved within 1 week after cessation of methimazole treatment. Immunologic abnormalities associated with methimazole treatment included the development of antinuclear antibodies in 52 of 238 (21.8%) cats tested and red cell autoantibodies (as evidenced by positive direct antiglobulin tests) in three of 160 (1.9%) cats tested.(ABSTRACT TRUNCATED AT 250 WORDS)
Peterson
M E
ME
Department of Medicine, Animal Medical Center, New York, NY 10021.
Kintzer
P P
PP
Hurvitz
A I
AI
D000818:Animals; D000974:Antibodies, Antinuclear / Q000032:analysis; D001323:Autoantibodies / Q000032:analysis; D002371:Cat Diseases / Q000188:drug therapy*; D002415:Cats; D004912:Erythrocytes / Q000276:immunology; D005260:Female; D006980:Hyperthyroidism / Q000188:drug therapy / Q000662:veterinary*; D008297:Male; D008713:Methimazole / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D013974:Thyroxine / Q000097:blood; D013997:Time Factors
D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D008713:Methimazole; D013974:Thyroxine