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# Megestrol Acetate ## Overview Megestrol acetate is a synthetic progestin. ## Primary Indications * **Oncology:** Treatment of advanced breast cancer and advanced endometrial cancer. * **Cachexia/Anorexia:** Treatment of anorexia, cachexia, or unexplained weight loss in patients with acquired immunodeficiency syndrome (AIDS). ## Adult Dosing * **Advanced Breast Cancer:** * 20 mg orally once daily. May be increased to 40 mg to 120 mg once daily. * **Advanced Endometrial Cancer:** * 40 mg to 320 mg orally once daily in divided doses. * **Cachexia/Anorexia (AIDS):** * 800 mg orally once daily. ## Pediatric Dosing There is no established pediatric dosing for megestrol acetate. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are recommended. * **Hepatic Impairment:** No specific dose adjustments are recommended, but caution is advised. ## Contraindications * Known hypersensitivity to megestrol acetate or any component of the formulation. * Pregnancy. ## Adverse Effects * **Common:** Weight gain, increased appetite, hypertension, hot flashes, rash, nausea, diarrhea, dyspnea, abdominal pain, fatigue, edema. * **Serious:** Adrenal insufficiency (especially with abrupt withdrawal), thromboembolic events (e.g., deep vein thrombosis, pulmonary embolism), hyperglycemia, Stevens-Johnson syndrome, toxic epidermal necrolysis. ## 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:** May affect glycemic control. ## Monitoring * **Tumor Response:** Based on cancer type and stage. * **Weight and Appetite:** Particularly in cachexia indications. * **Blood Pressure:** Due to risk of hypertension. * **Electrolytes:** Especially if prolonged use or signs of adrenal insufficiency. * **Blood Glucose:** In patients with diabetes or at risk. * **Signs of Thromboembolic Events:** Leg swelling, pain, shortness of breath. * **Adrenal Function:** If abrupt discontinuation is considered after prolonged therapy. ## Clinical Pearls * Megestrol acetate is a potent appetite stimulant and can lead to significant weight gain. * Abrupt discontinuation after long-term use may lead to adrenal insufficiency. Gradual tapering may be necessary. * Use with caution in patients with a history of thromboembolic events. * Due to potential for fetal harm, adequate contraception is essential for patients of childbearing potential. *** **Disclaimer:** This information is intended for clinical professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines for complete details and to ensure appropriate patient care.