The U.S. Food and Drug Administration has approved Dechra Ltd.’s Felimazole (methimazole), the first drug approved for the treatment of hyperthyroidism in cats.
“Hyperthyroidism is one of the most common diseases seen in middle-aged and senior cats,” said Bernadette Dunham, DVM, Ph.D., director of FDA’s Center for Veterinary Medicine. “Cats can become seriously ill with this condition. The approval of Felimazole offers cat owners, in consultation with their veterinarians, an effective medical treatment for this serious disease.”
Methimazole has been used to treat feline hyperthyroidism for years, but because it is a drug for humans, its use in animals has been off-label.
Field studies evaluating the effectiveness and safety of the product were conducted in the United Kingdom and the United States. Success was measured by a decrease in the production of thyroid hormones or T4 levels and improvement in clinical signs, such as weight gain, cessation of vomiting and regaining normal eating habits.
A total of 166 hyperthyroid cats were treated with Felimazole. In the U.K. study, 77 percent of cats had normal T4 levels and 81 percent had reduced disease severity by day 42. In the U.S. study, 61 percent of cats were considered treatment successes with a significant decrease in T4 concentration and improved clinical signs by day 42.
The most common side effects associated with the drug include a change in food consumption (increase or decrease), lethargy, vomiting and diarrhea. Less common side effects include anemia and low platelet count in some cats, according to the FDA.
Dechra Ltd. is based in Staffordshire, United Kingdom , with U.S. operations based in Overland Park, Kan.