Megestrol acetate tablets are indicated for the palliative treatment of advanced breast and endometrial cancer (i.e., patients with recurrent, inoperable, or metastatic disease). The precise mechanism of the antitumor effect of megestrol acetate in endometrial cancer is unknown, but has been hypothesized to be an antiprogesterone effect regulated through the pituitary gland. There is also evidence suggesting a localized effect, i.e., an effect due to marked changes caused by injecting a progesterone-based agent directly into the endometrial cavity. Similarly, the mechanism of the antitumor effect of this product in breast cancer is unclear. The most common adverse effect of this product is weight gain, and nausea and vomiting may also be present. It is not a substitute for currently received surgery, radiation or chemotherapy. Contraindicated in persons who are hypersensitive to any component of this species. It is contraindicated in cases of severe hepatic insufficiency; patients with thrombophlebitis and thrombosis; and diagnostic tests for pregnancy. The drug is prescribed and should be used in strict compliance with the doctor’s instructions.