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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic progestin derivative used primarily for its appetite stimulant and anti-neoplastic effects.
## Primary Indications
* Management of anorexia, cachexia, or unexplained significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced breast cancer and endometrial cancer.
## Adult Dosing
* **Appetite Stimulation/Weight Gain:**
* Oral suspension: 625 mg (25 mL) once daily. Doses up to 1250 mg daily have been used.
* Oral tablets: 40 mg, 160 mg, or 320 mg once daily. Common doses range from 160 mg to 800 mg daily.
* **Breast Cancer:**
* 160 mg once daily.
* **Endometrial Cancer:**
* 40 mg four times daily (total 160 mg daily). Treatment may be continued for at least 2 months.
## Pediatric Dosing
There is no established pediatric dosing for megestrol acetate.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are recommended.
* **Hepatic Impairment:** No specific dose adjustments are recommended, but caution is advised.
## Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy.
## Adverse Effects
* **Common:** Weight gain (often due to fluid retention), increased appetite, hot flashes, hypertension, dyspnea, nausea, vomiting, diarrhea, abdominal pain, rash, edema, fatigue.
* **Serious:** Adrenal insufficiency, thromboembolic events (deep vein thrombosis, pulmonary embolism), hyperglycemia, new-onset diabetes, exacerbation of existing diabetes, tumor flare (in hormone-sensitive cancers), Cushing's syndrome.
## Key Drug Interactions
* **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations.
* **CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole, erythromycin):** May increase megestrol acetate concentrations.
## Monitoring
* **Weight and appetite:** Regularly assess for effectiveness.
* **Blood glucose:** Especially in patients with diabetes or risk factors.
* **Adrenal function:** Monitor for signs of adrenal insufficiency (fatigue, weakness, nausea, vomiting, hypotension), particularly with prolonged use or abrupt discontinuation.
* **Thromboembolic events:** Monitor for signs and symptoms of DVT or PE (leg pain/swelling, sudden shortness of breath, chest pain).
* **Blood pressure:** Monitor for hypertension.
## Clinical Pearls
* Oral suspension is typically preferred for appetite stimulation due to easier administration and potential for higher doses.
* Gradual dose reduction is recommended upon discontinuation to minimize withdrawal symptoms.
* Women of childbearing potential should use effective contraception during treatment.
* May cause adrenal suppression; abrupt discontinuation should be avoided.
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**Disclaimer:** This information is intended for clinical decision support and does not replace a thorough review of the current prescribing information or consultation with other healthcare professionals. Always verify the latest product monograph and guidelines before prescribing.
