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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic progestin derivative.
## Primary Indications
* Treatment of cachexia, anorexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced endometrial carcinoma and breast carcinoma.
## Adult Dosing
* **AIDS-associated cachexia:** Typically initiated at 800 mg daily, given as a single dose or divided into two doses. Doses may be adjusted based on clinical response and tolerability.
* **Endometrial carcinoma:** Typically 40 mg four times daily (160 mg daily). Treatment may be continued as long as the patient is benefiting.
* **Breast carcinoma:** Typically 160 mg daily.
## Pediatric Dosing
There is no established pediatric dosing for megestrol acetate. Its use in children is generally not recommended due to lack of data and potential risks.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are recommended, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustments are recommended, but caution is advised.
## Contraindications
* Known or suspected pregnancy.
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Undiagnosed abnormal vaginal bleeding.
## Adverse Effects
Common adverse effects include: weight gain, diarrhea, nausea, vomiting, abdominal pain, rash, alopecia, hot flashes, and edema. Serious adverse effects can include: thromboembolic events (deep vein thrombosis, pulmonary embolism), adrenal insufficiency, hyperglycemia, and new-onset diabetes mellitus.
## Key Drug Interactions
* **CYP3A4 inhibitors (e.g., ritonavir, ketoconazole):** May increase megestrol acetate concentrations. Monitor for increased adverse effects.
* **CYP3A4 inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations. Monitor for decreased efficacy.
* **Aminoglutethimide:** May decrease megestrol acetate concentrations.
## Monitoring
* Weight and appetite.
* Signs and symptoms of thromboembolic events (e.g., leg pain/swelling, shortness of breath).
* Blood glucose levels, especially in patients with diabetes or risk factors for diabetes.
* Adrenal function if therapy is to be discontinued abruptly, particularly after prolonged use.
## Clinical Pearls
* Megestrol acetate is a potent appetite stimulant.
* Significant weight gain is a common side effect.
* Use in children is not recommended due to limited safety and efficacy data and potential for long-term endocrine disruption.
* Patients should be counseled on the risk of thromboembolic events and adrenal insufficiency.
* Gradual tapering may be considered after prolonged therapy to avoid adrenal insufficiency.
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**Disclaimer:** This information is intended for clinical use by healthcare professionals. It is not exhaustive and does not replace a thorough review of the full prescribing information, institutional protocols, or individual patient assessment. Always verify current prescribing information before making clinical decisions.
