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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:** 625 mg (25 mL) orally once daily. Higher doses (up to 1250 mg daily) may be considered, but evidence for increased benefit is limited.
* **Breast cancer:** 160 mg orally once daily.
* **Endometrial cancer:** 40 mg orally 4 times daily.
### Pediatric Dosing
* There is no established pediatric dosing for megestrol acetate. Use in pediatric patients is generally not recommended due to limited data and potential risks.
### Dose Adjustments
* No specific dose adjustments are recommended for hepatic or renal impairment. However, caution is advised in patients with pre-existing liver disease.
### Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy: Megestrol acetate is contraindicated in pregnancy due to potential for fetal harm.
### Adverse Effects
* **Common:** Weight gain, increased appetite, hypertension, hot flashes, rash, nausea, diarrhea, dyspnea.
* **Serious:** Adrenal insufficiency (especially with abrupt discontinuation after prolonged use), thromboembolic events (deep vein thrombosis, pulmonary embolism), hyperglycemia, new onset diabetes, exacerbation of existing diabetes, Stevens-Johnson syndrome, toxic epidermal necrolysis.
### Key Drug Interactions
* **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations.
* **CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole):** May increase megestrol acetate concentrations.
* **Other Progestins:** Additive effects may occur.
### Monitoring
* **Weight and appetite:** Regularly monitor for changes.
* **Blood pressure:** Monitor for hypertension.
* **Blood glucose:** Monitor for hyperglycemia, especially in patients with diabetes or risk factors.
* **Electrolytes:** Monitor as clinically indicated.
* **Signs of thromboembolism:** Educate patients on symptoms (e.g., leg swelling, shortness of breath, chest pain) and monitor closely.
* **Adrenal function:** Consider monitoring for adrenal insufficiency, particularly if tapering or discontinuing therapy after prolonged use.
### Clinical Pearls
* Onset of action can be slow; significant clinical benefit may not be apparent for several weeks.
* Abrupt discontinuation after prolonged use can lead to adrenal insufficiency. Tapering may be necessary.
* Weight gain may be due to fluid retention as well as increased fat and lean body mass.
* Use with caution in patients with a history of thromboembolic disorders.
* Contraception: Advise patients of reproductive potential to use effective contraception during treatment.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details.*
