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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic progestin.
## Primary Indications
* **Cachexia, anorexia, or unexplained weight loss:** Primarily associated with conditions like acquired immunodeficiency syndrome (AIDS) or cancer.
* **Palliative treatment of advanced breast cancer or endometrial cancer.**
## Adult Dosing
* **Cachexia/Anorexia:**
* Initial dose: 400-800 mg daily.
* Maintenance dose: Often 400 mg daily, but may range from 100-1200 mg daily depending on patient response and tolerance. Doses are typically divided, but can be given once daily.
* **Breast Cancer:** 160 mg daily.
* **Endometrial Cancer:** 40 mg, 4 times daily (160 mg daily).
## Pediatric Dosing
There is **no established pediatric dosing** for megestrol acetate.
## 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 or suspected hypersensitivity to megestrol acetate or any component of the formulation.
## Adverse Effects
* **Common:** Weight gain (often desired in cachexia), increased appetite, nausea, vomiting, diarrhea, abdominal pain, hot flashes, hypertension, rash, edema, dyspnea, carpal tunnel syndrome, vaginal bleeding, amenorrhea, impotence.
* **Serious:** Thromboembolic events (e.g., pulmonary embolism, deep vein thrombosis), adrenal insufficiency (especially with abrupt withdrawal after prolonged use), hyperglycemia, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **CYP3A4 Inhibitors/Inducers:** May alter megestrol acetate concentrations. Monitor for altered efficacy or toxicity. Examples include ketoconazole, itraconazole, rifampin, phenytoin.
* **Aminoglutethimide:** May decrease megestrol acetate concentrations.
## Monitoring
* **Weight and appetite:** Especially in patients being treated for cachexia.
* **Electrolytes:** Sodium, potassium, glucose.
* **Adrenal function:** Consider if symptoms of adrenal insufficiency arise, particularly with abrupt discontinuation after prolonged use or in patients with concurrent adrenal suppression.
* **Signs of thromboembolic events.**
* **Blood pressure.**
* **Menstrual irregularities and signs of pregnancy in premenopausal women.**
## Clinical Pearls
* Megestrol acetate can cause significant weight gain, primarily through increased appetite.
* It is crucial to counsel patients about the potential for adrenal insufficiency with abrupt discontinuation, especially after long-term use. Gradual tapering may be necessary.
* Women of childbearing potential should use effective non-hormonal contraception.
* The oral suspension may be preferred for ease of administration and potentially better absorption compared to tablets in some patients.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines for complete details, including contraindications, warnings, precautions, adverse reactions, and drug interactions, before making any treatment decisions. Dosing may vary based on individual patient factors and local protocols.
