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# Megestrol Acetate (Megace ES, Megace)
## Overview
Megestrol acetate is a synthetic derivative of progesterone.
## Primary Indications
* Management of cachexia, anorexia, or unexplained weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced breast cancer.
* Palliative treatment of advanced endometrial cancer.
## Adult Dosing
* **AIDS-associated wasting/anorexia:**
* Oral suspension (40 mg/mL): 625 mg orally once daily.
* Tablets (200 mg or 400 mg): 800 mg orally once daily.
* **Advanced breast cancer:** 160 mg orally once daily.
* **Advanced endometrial cancer:** 40 mg orally four times daily (160 mg/day).
## Pediatric Dosing
Dosing for pediatric patients has not been established.
## Dose Adjustments
* No specific dose adjustments are recommended for hepatic or renal impairment. However, caution should be exercised in patients with pre-existing conditions.
## Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy.
## Adverse Effects
* **Common:** Weight gain (often due to fluid retention and increased appetite), hot flashes, hypertension, rash, diarrhea, nausea, shortness of breath, headache, carpal tunnel syndrome.
* **Serious:** Adrenal insufficiency (especially with abrupt withdrawal), thromboembolic events (deep vein thrombosis, pulmonary embolism, stroke, myocardial infarction), hyperglycemia, vision changes, new onset diabetes mellitus.
## Key Drug Interactions
* **CYP3A4 inhibitors:** May increase megestrol acetate concentrations. Examples include ritonavir and other protease inhibitors.
* **CYP3A4 inducers:** May decrease megestrol acetate concentrations. Examples include rifampin, carbamazepine, and phenytoin.
* **Corticosteroids:** Increased risk of adrenal suppression.
## Monitoring
* Weight and appetite.
* Blood pressure.
* Signs and symptoms of thromboembolic events.
* Electrolytes, glucose, and adrenal function (especially with prolonged use or abrupt discontinuation).
* Vision changes.
## Clinical Pearls
* Appetite stimulation and weight gain are common and often the desired effects for AIDS-associated wasting.
* Thromboembolic events are a significant risk, particularly in patients with underlying risk factors.
* Adrenal insufficiency can occur, especially with long-term use and abrupt cessation. Consider gradual tapering if discontinuing therapy.
* Contraception is essential for women of childbearing potential due to the risk of fetal harm.
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**Disclaimer:** This information is intended for clinical professionals. Always verify current prescribing information and institutional protocols before making any treatment decisions.
