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# Megestrol Acetate (Megestrol)
## Overview
Megestrol acetate is a synthetic progestogen with antineoplastic and antiestrogenic properties. It is also used as an appetite stimulant.
## Primary Indications
* **Cancer therapy:** Palliative treatment of advanced breast cancer in postmenopausal women.
* **Appetite stimulation:** Treatment of anorexia, cachexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
## Adult Dosing
* **Breast Cancer:** 160 mg daily. Higher doses (e.g., 400-800 mg daily) have been used, but efficacy at higher doses is not definitively established and side effects may increase.
* **Appetite Stimulation (AIDS):**
* Initial dose: 400 mg (400 mL) daily.
* May be administered as 200 mg (200 mL) twice daily, or 400 mg (400 mL) once daily.
* Doses can be increased to 800 mg daily if appetite does not improve.
## Pediatric Dosing
* There is **no established pediatric dosing** for megestrol acetate. Its use in children is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are routinely recommended, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustments are routinely recommended, but caution is advised.
## Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy.
* Undiagnosed abnormal vaginal bleeding.
* Thrombophlebitis, a history of or current arterial or venous thromboembolism or cerebrovascular accident.
## Adverse Effects
* **Common:** Weight gain, increased appetite, nausea, vomiting, diarrhea, abdominal pain, hot flashes, dyspnea, edema, hypertension, rash, headache, fatigue, mood changes.
* **Serious:** Thromboembolic events (deep vein thrombosis, pulmonary embolism, stroke, myocardial infarction), adrenal insufficiency, hyperglycemia, tumor flare (transient increase in tumor size).
## Key Drug Interactions
* **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease plasma concentrations of megestrol acetate.
* **CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole, erythromycin):** May increase plasma concentrations of megestrol acetate.
* **Aminoglutethimide:** May decrease plasma concentrations of megestrol acetate.
* **Insulin and oral hypoglycemic agents:** May require adjustment due to potential for hyperglycemia.
## Monitoring
* **Breast Cancer:** Monitor for tumor response, signs of thromboembolism, adrenal insufficiency, and adverse effects.
* **Appetite Stimulation:** Monitor weight, appetite, nutritional status, and signs of thromboembolism and adrenal insufficiency.
* **Routine:** Monitor blood pressure, electrolytes, glucose, and hepatic function tests periodically.
## Clinical Pearls
* Megestrol acetate can cause significant weight gain due to increased appetite.
* Be aware of the risk of adrenal insufficiency, especially with long-term use or abrupt discontinuation. Patients on long-term therapy may require corticosteroid supplementation during periods of stress (e.g., surgery, illness).
* Thromboembolic events are a serious concern; patients should be advised to report symptoms such as leg pain or swelling, sudden shortness of breath, chest pain, or sudden severe headache.
* Use in pregnancy is contraindicated due to potential fetal harm.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for complete details before making any treatment decisions.
