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# Megestrol Acetate (Megace) ## Overview Megestrol acetate is a synthetic progestin. It is believed to exert its effects by inhibiting cellular proliferation and by altering the production and release of endogenous hormones. ## Primary Indications * **Cachexia, anorexia, or unexplained significant weight loss:** In patients with acquired immunodeficiency syndrome (AIDS). * **Palliative treatment of advanced breast cancer:** In postmenopausal women. ## Adult Dosing * **Cachexia/Anorexia/Weight Loss (AIDS):** * Oral suspension: 625 mg (25 mL) once daily. Higher doses up to 1250 mg daily have been used. * Tablets: 40 mg four times daily (160 mg/day). Increased doses up to 1250 mg daily have been used. * **Advanced Breast Cancer:** * Oral suspension: 160 mg (40 mL) once daily. * Tablets: 40 mg four times daily (160 mg/day). Doses may be increased to 80 mg four times daily (320 mg/day). ## Pediatric Dosing There is no established pediatric dosing for megestrol acetate. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustment is recommended. * **Hepatic Impairment:** No specific dose adjustment is recommended; however, caution is advised. ## Contraindications * Known hypersensitivity to megestrol acetate or any component of the formulation. * Pregnancy. ## Adverse Effects * **Common:** Weight gain, increased appetite, headache, nausea, vomiting, diarrhea, abdominal pain, hot flashes, rash, hypertension, dyspnea, alopecia, edema, carpal tunnel syndrome. * **Serious:** Adrenal insufficiency (especially with abrupt withdrawal after prolonged use), thromboembolic events (pulmonary embolism, deep vein thrombosis), hyperglycemia, new onset or worsening of diabetes mellitus, depression, Stevens-Johnson syndrome, toxic epidermal necrolysis. ## Key Drug Interactions * **Aminoglutethimide:** May decrease megestrol acetate concentrations. * **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations. * **Antidiabetic agents:** Megestrol acetate can cause hyperglycemia and may require adjustment of antidiabetic medications. ## Monitoring * **Weight and appetite:** Regularly monitor for signs of weight gain and increased appetite. * **Adrenal function:** Consider monitoring adrenal function, particularly if the drug is withdrawn abruptly after prolonged use, or in situations of stress or illness. * **Thromboembolic events:** Monitor for signs and symptoms of deep vein thrombosis or pulmonary embolism. * **Blood glucose:** Monitor blood glucose levels, especially in patients with diabetes or at risk for hyperglycemia. * **Mental status:** Monitor for signs of depression or other mood changes. ## Clinical Pearls * Abrupt discontinuation after prolonged use may lead to adrenal insufficiency. Taper the dose gradually if discontinuing. * Weight gain is a common and expected effect, particularly in patients with AIDS-related wasting. * Monitor patients closely for signs of thromboembolic events and hyperglycemia. * The oral suspension may be preferred for ease of administration in some patients. *** *This information is intended for healthcare professionals and does not substitute for consulting the most current prescribing information from the manufacturer or other reliable sources before making clinical decisions.*