The oral administration of megestrol acetate to postpone oestrus in cats

During 1974, megestrol acetate tablets were distributed to 397 cat owners in the Oslo district for use as an oestrus suppressing agent in cats. A weekly dose of 2.5 mg megestrol acetate was given for at least 30 weeks. Treatment was carried out according to plan in 244 cats. Results are shown in Table I. The course of birth was abnormal in two cats which were pregnant before the trial began. Pregnancy was not registered in any of the remainder. Heat was observed during the period of treatment in 21 of the 244 cats treated according to plan without pregnancy being registered. As regards side effects of the preparation, increased appetite, weight increase and changes of temperament were the most pronounced. One cat developed pyometra after three years of treatment with the preparation.