Mezest 160 mg contains Megestrol Acetate, a synthetic progestin with antineoplastic and progestational properties. It is primarily used for the palliative treatment of advanced carcinoma of the breast and endometrium, as well as for managing anorexia, cachexia, or significant weight loss in patients with AIDS or cancer. Megestrol Acetate works by inhibiting estrogen synthesis and may have a direct cytotoxic effect on tumor cells. It is typically administered once daily for breast cancer or in higher doses for weight loss and cachexia associated with serious illnesses.