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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic derivative of progesterone.
## Primary Indications
* Treatment of cachexia, anorexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced breast cancer.
* Palliative treatment of advanced endometrial cancer.
## Adult Dosing
* **AIDS-related cachexia/anorexia:** 800 mg orally once daily. A lower dose of 400 mg/day may be effective for some patients, with doses ranging from 100-800 mg/day.
* **Advanced breast cancer:** 160 mg orally once daily.
* **Advanced endometrial cancer:** 40 mg orally 4 times daily (160 mg/day).
## Pediatric Dosing
Dosing has not been established in pediatric patients.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are routinely recommended.
* **Hepatic Impairment:** No specific dose adjustments are routinely recommended.
## 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, nausea, diarrhea, rash, dyspnea, edema.
* **Serious:** Thrombotic events (e.g., pulmonary embolism, deep vein thrombosis), adrenal insufficiency (especially with abrupt discontinuation after prolonged use), hyperglycemia, new onset or worsening of diabetes mellitus, depression, alopecia, carpal tunnel syndrome.
## Key Drug Interactions
* **CYP3A4 inducers (e.g., rifampin, phenytoin, phenobarbital):** May decrease megestrol acetate plasma concentrations.
* **CYP3A4 inhibitors (e.g., ketoconazole, ritonavir):** May increase megestrol acetate plasma concentrations.
* **Aminoglutethimide:** May decrease megestrol acetate plasma concentrations.
## Monitoring
* **Weight and appetite:** To assess therapeutic response.
* **Blood pressure:** To monitor for hypertension.
* **Electrolytes, glucose, and A1c:** Particularly in patients with diabetes or at risk.
* **Signs of adrenal insufficiency:** Especially if discontinued after prolonged high-dose therapy.
* **Signs and symptoms of thromboembolic events:** (e.g., leg pain, swelling, chest pain, shortness of breath).
## Clinical Pearls
* Megestrol acetate can cause significant appetite stimulation and weight gain, which may be beneficial in cachectic patients but can be problematic in others.
* Abrupt discontinuation after prolonged use, especially at high doses, can lead to adrenal insufficiency. Tapering the dose may be necessary.
* Use with caution in patients with a history of thrombotic events.
* Contraception should be used by women of childbearing potential.
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*This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant literature for definitive guidance before making clinical decisions.*
