MegestrolDose, contraindications and adverse effects for Cats, Dogs and Horses.

Synthetic progestin hormone; used historically for estrus suppression and some dermatologic/behavioral conditions, now used cautiously given its side-effect… Megestrol is FDA-approved for use in dogs for the postponement of estrus and the alleviation of pseudopregnancy; however, it has fallen out of favor for treatment of pseudopregnancy due to recurrence rates after drug withdrawal, adverse effects associated with its use, and availability of safer options (eg, cabergoline). In male dogs, it has also been used for benign prostatic hypertrophy. Meges

Megestrol possesses the pharmacologic actions expected of other progestational drugs (eg, medroxyprogesterone acetate). It has significant antiestrogen and glucocorticoid activity (with resultant adrenal suppression). It does not have anabolic or masculinizing effects on the developing fetus.

Megestrol is contraindicated in pregnant animals or in animals with uterine disease, diabetes mellitus, or mammary neoplasias. Mege- strol is not recommended in dogs prior to their first estrous cycle or for anestrus therapy in dogs with abnormal cycles. Prevent mating if estrus occurs within 30 days of cessation of megestrol therapy. Megestrol should not be used during pregnancy

Adverse effects in dogs include increased appetite, weight gain, lethargy, change in behavior, change in hair color, mucometra, endometritis, pyometra, cystic endometrial hyperplasia, mammary enlargement and neoplasia, acromegaly, adrenocortical suppression, and, rarely, lactation. One dog reportedly developed diabetes mellitus after use. Adverse effects in cats include profound adrenocortical suppression and adrenal atrophy.

■ Body weight ■ Baseline and periodic blood glucose ■ Mammary gland development and appearance ■ Adrenocortical function (ie, ACTH stimulation) with long-term treatment ■ Liver enzymes if long-term treatment ■ Efficacy