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## Overview
Megestrol acetate is a synthetic progestin used primarily for palliative treatment of cachexia and anorexia associated with acquired immunodeficiency syndrome (AIDS) and advanced malignancies. It is also used for hormone-responsive advanced breast and endometrial cancers.
## Primary Indications
* Treatment of anorexia, cachexia, or unexplained, significant weight loss in patients with acquired immunodeficiency syndrome (AIDS).
* Palliative treatment of advanced breast cancer.
* Palliative treatment of advanced endometrial carcinoma.
## Adult Dosing
* **AIDS-related cachexia/anorexia:** 800 mg orally once daily. Higher doses (e.g., 1600 mg daily) have been used but do not appear to offer significant additional benefit.
* **Breast cancer:** 160 mg orally once daily.
* **Endometrial carcinoma:** 40 mg orally four times daily (40 mg PO QID), or 160 mg orally once daily.
## Pediatric Dosing
There is **no established pediatric dosing** for megestrol acetate. Its use in this population is generally not recommended due to lack of safety and efficacy data.
## Dose Adjustments
No specific dose adjustments are routinely required based on renal or hepatic impairment. However, caution and close monitoring are advised in patients with severe hepatic impairment.
## Contraindications
* Known or suspected pregnancy.
* Known hypersensitivity to megestrol acetate.
* Undiagnosed abnormal vaginal bleeding.
## Adverse Effects
* **Common:** Weight gain, increased appetite, nausea, vomiting, diarrhea, hot flashes, hypertension, edema, dyspnea, rash, headache, mood changes.
* **Serious:** Thrombotic events (e.g., pulmonary embolism, deep vein thrombosis), adrenal insufficiency, hyperglycemia, Cushing's syndrome, Stevens-Johnson syndrome.
* **Endocrine:** Menstrual irregularities, decreased libido, impotence.
## 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.
* **Aminoglutethimide:** May decrease megestrol acetate concentrations.
## Monitoring
* Weight and appetite changes.
* Signs and symptoms of thrombotic events.
* Blood pressure.
* Signs of adrenal insufficiency (especially in patients with conditions affecting the adrenal glands or those discontinuing corticosteroids).
* Blood glucose, particularly in diabetic patients.
* Pregnancy status in women of childbearing potential.
## Clinical Pearls
* Megestrol acetate is a potent appetite stimulant and can lead to significant weight gain, which may not be lean body mass.
* The risk of thrombotic events is increased, especially with higher doses or prolonged use.
* Due to potential adrenal suppression, patients should not discontinue megestrol acetate abruptly, particularly if they have been on concurrent corticosteroid therapy. Tapering may be necessary.
* Counsel patients regarding the potential for menstrual irregularities, decreased libido, and impotence.
* For AIDS-related cachexia, treatment is palliative and intended to improve quality of life rather than cure the underlying disease.
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**Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always verify current prescribing information and consult with the relevant healthcare provider or specialist before making any treatment decisions. Dosing and indications may vary based on local protocols and individual patient circumstances.
