- Class: Progestin – synthetic progestogen
- Route: Oral suspension or tablet
Mechanism of Action (MOA)
- Progestogenic activity: binds progesterone receptors → alters gene transcription
- Reduces gonadotropin release, may have anti-estrogen effects in some tissues
- Exhibits appetite-stimulating (orexigenic) effects, mechanism not fully understood
Clinical Uses
- Anorexia/cachexia in cancer or AIDS patients – stimulates appetite and weight gain
- Palliative treatment of advanced breast cancer or endometrial carcinoma – hormone therapy
- Off-label: endometriosis, prevention of endometrial hyperplasia
Dosing (Adults)
- Cancer-related anorexia/cachexia: 160–320 mg orally daily
- Breast or endometrial cancer: 40–320 mg orally daily (depending on regimen)
- Administer with or without food
- Dose adjustments: typically not needed for renal or hepatic impairment, but monitor clinically
Toxicities
- Endocrine/metabolic: weight gain, fluid retention, thromboembolic events
- Gastrointestinal: nausea, vomiting, diarrhea
- Neurologic: headache, insomnia, mood changes
- Rare: adrenal suppression with prolonged high doses
- Caution in patients at risk for venous thromboembolism
Monitoring
- Weight and nutritional status
- Signs of fluid retention or edema
- Blood pressure and thromboembolic risk factors
- Liver function tests if long-term therapy
Summary
Megestrol acetate (Megace®) is a synthetic progestin used for cancer- or AIDS-related cachexia and certain hormone-sensitive cancers. Key concerns are weight gain, fluid retention, thromboembolism, and endocrine effects, requiring monitoring of weight, fluid status, and thrombotic risk.