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## Megestrol Acetate
### Overview
Megestrol acetate is a synthetic progestin. It is available in oral suspension and tablet formulations.
### Primary Indications
* Treatment of anorexia, cachexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced carcinoma of the breast or endometrium.
### Adult Dosing
* **AIDS-related anorexia/cachexia:**
* Oral Suspension: 625 mg (25 mL) orally once daily. Higher doses may be required.
* Tablets: 625 mg orally once daily.
* *Note:* Doses of 100 mg to 1000 mg per day have been used. The optimal dose is not established and depends on patient response.
* **Breast cancer:**
* 40 mg (10 mL) orally four times daily.
* Alternatively, 160 mg (64 mL) orally once daily.
* **Endometrial cancer:**
* 40 mg (10 mL) orally four times daily.
* Alternatively, 160 mg (64 mL) orally once daily.
* Treatment should continue for at least 2 months to determine therapeutic efficacy.
### Pediatric Dosing
Dosing has not been established in pediatric patients.
### Dose Adjustments
* **Hepatic Impairment:** No specific dosage adjustments are recommended. Monitor patients closely.
* **Renal Impairment:** No specific dosage adjustments are recommended. Monitor patients closely.
### Contraindications
* Known or suspected pregnancy.
* Known hypersensitivity to megestrol acetate or any component of the formulation.
### Adverse Effects
* **Common:** Weight gain, increased appetite, hypertension, hot flashes, rash, diarrhea, nausea, shortness of breath, fluid retention (edema), headache, insomnia, and fatigue.
* **Serious:** Thrombophlebitis and thromboembolic phenomena (e.g., pulmonary embolism, deep vein thrombosis), adrenal insufficiency (especially with abrupt discontinuation), hyperglycemia, new-onset diabetes, exacerbation of existing diabetes, and vaginal bleeding.
* **Malignancy:** May have a potential for teratogenicity and fetal harm.
### Key Drug Interactions
* **CYP3A4 Inhibitors/Inducers:** Megegestrol acetate is a substrate of CYP3A4. Concurrent use with strong CYP3A4 inhibitors may increase megestrol acetate concentrations. Concurrent use with strong CYP3A4 inducers may decrease megestrol acetate concentrations.
* **Diabetes Medications:** May worsen glycemic control. Close monitoring of blood glucose is necessary. Dose adjustments of antidiabetic agents may be required.
### Monitoring
* **Weight and appetite:** Assess for effectiveness.
* **Blood pressure:** Monitor for hypertension.
* **Electrolytes:** Monitor for fluid retention and electrolyte imbalances.
* **Blood glucose:** Especially in patients with diabetes or at risk.
* **Signs of thromboembolic events:** Monitor for leg pain, swelling, chest pain, or shortness of breath.
* **Adrenal function:** Monitor for signs of adrenal insufficiency, particularly upon discontinuation.
### Clinical Pearls
* Weight gain may be primarily due to fluid retention and increased fat mass.
* The effect on appetite is often observed within the first few weeks of treatment.
* Gradual tapering of the dose is recommended upon discontinuation, especially after prolonged use, to minimize the risk of adrenal insufficiency.
* Counsel patients on potential adverse effects, including thromboembolic events and worsening glycemic control.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.
