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# Megestrol Acetate (Megace ES, Megace) ## Overview Megestrol acetate is a synthetic progestin used to treat cachexia, anorexia, and unexplained weight loss associated with chronic conditions like AIDS and cancer. It also has a history of use in palliative care for certain hormone-responsive cancers. ## Primary Indications * Treatment of anorexia, cachexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS). * Palliative treatment of advanced breast cancer and endometrial carcinoma (less common currently). ## Adult Dosing * **Cachexia/Anorexia (AIDS-related):** * Oral suspension (40 mg/mL): 625 mg (approximately 15.6 mL) orally once daily. * Tablets (20 mg or 40 mg): 800 mg orally once daily. * *Note:* Dosing can vary. Some protocols may start at lower doses and titrate up. Maximum daily doses typically range from 800 mg to 1200 mg. Consult local protocol for specific titration guidance. ## Pediatric Dosing There is no established pediatric dosing for megestrol acetate. Its use in pediatric populations is generally not recommended due to lack of data and potential risks. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are established. Caution is advised. * **Hepatic Impairment:** No specific dose adjustments are established. Caution is advised. ## Contraindications * Known or suspected pregnancy. * Known hypersensitivity to megestrol acetate or any component of the formulation. ## Adverse Effects * **Common:** Weight gain (often fluid retention), increased appetite, nausea, vomiting, diarrhea, hot flashes, hypertension, rash, shortness of breath, headache, hyperglycemia. * **Serious:** Thromboembolic events (e.g., deep vein thrombosis, pulmonary embolism), adrenal insufficiency (especially with abrupt discontinuation after prolonged use), new-onset diabetes, tumor flare. ## Key Drug Interactions * **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations. * **CYP3A4 Inhibitors (e.g., ketoconazole, erythromycin):** May increase megestrol acetate concentrations. * **Antidiabetic Agents:** Megestrol acetate can cause hyperglycemia, potentially requiring adjustment of antidiabetic medications. ## Monitoring * Weight and appetite. * Signs and symptoms of adrenal insufficiency (fatigue, weakness, nausea, vomiting, hypotension). * Blood glucose levels, especially in patients with diabetes or risk factors. * Signs of thromboembolic events. * Electrolytes. ## Clinical Pearls * Dosing for cachexia/anorexia is often higher than historically used for cancer indications. * Significant weight gain is a common and often desired effect, but can be due to fluid retention. * Abrupt discontinuation after long-term use may lead to adrenal insufficiency. Tapering may be necessary. * May cause menstrual irregularities in premenopausal women. * Use with caution in patients with a history of thromboembolic disease. *** *Disclaimer: This information is intended for clinical decision support and does not replace professional judgment. Always consult the most current prescribing information and relevant literature for complete details before making treatment decisions.*