The active ingredient in EX-5, megestrol acetate, affects the hypothalamic-pituitary system, blocking the secretion of gonadotropic hormones (FSH and LH). This provides anti-estrogenic and anti-ovulatory effects on the gonads of animals, resulting in the suppression of sexual heat. Megestrol acetate also exhibits significant anti-glucocorticoid activity. It is well absorbed from the gastrointestinal tract, metabolized in the liver to conjugates, and excreted (as metabolites) via urine and feces. After discontinuation of the preparation, 90% of the total dose is excreted from the animal’s body within 15 days.