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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic progestin with antineoplastic and antiestrogenic properties. It is also known for its appetite-stimulating effects.
## Primary Indications
* **Palliative treatment of advanced carcinoma of the breast** in postmenopausal women.
* **Palliative treatment of advanced or metastatic carcinoma of the endometrium**.
* Management of **anorexia, cachexia, or unexplained significant weight loss** in patients with acquired immunodeficiency syndrome (AIDS).
## Adult Dosing
* **Breast Cancer:** 160 mg (40 mL) once daily.
* **Endometrial Carcinoma:** 40 mg (10 mL) four times daily. May be increased to 40 mg (10 mL) six times daily.
* **AIDS-associated Anorexia/Cachexia/Weight Loss:** 400-800 mg (100-200 mL) once daily.
## Pediatric Dosing
There is no established pediatric dosing for megestrol acetate. Use in pediatric populations is generally not recommended due to lack of safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are recommended, but caution may be warranted due to potential accumulation.
* **Hepatic Impairment:** No specific dose adjustments are recommended, but caution may be warranted.
## Contraindications
* Known or suspected **pregnancy**.
* Known or suspected **hypersensitivity** to megestrol acetate or any component of the formulation.
* Use in conditions where the effects of progestins are undesirable (e.g., undiagnosed vaginal bleeding, known or suspected breast or genital malignancy other than specific indications).
## Adverse Effects
* **Common:** Weight gain, increased appetite, hypertension, hot flashes, nausea, vomiting, diarrhea, abdominal pain, rash, dyspnea, edema, fatigue, amenorrhea, vaginal hemorrhage.
* **Serious:** Thromboembolic events (deep vein thrombosis, pulmonary embolism, stroke, myocardial infarction), adrenal insufficiency, hyperglycemia, vision disturbances.
* **Gastrointestinal:** Increased appetite, nausea, vomiting, diarrhea.
* **Endocrine:** Hot flashes, amenorrhea, vaginal hemorrhage.
## Key Drug Interactions
* **CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole, ritonavir):** May increase megestrol acetate concentrations, potentially increasing adverse effects. Monitor for increased adverse effects.
* **CYP3A4 Inducers (e.g., rifampin, phenytoin, carbamazepine):** May decrease megestrol acetate concentrations, potentially reducing efficacy. Monitor for reduced efficacy.
* **Aminoglutethimide:** May decrease megestrol acetate concentrations.
## Monitoring
* **For Cancer Indications:** Tumor response, signs and symptoms of disease progression.
* **For AIDS-associated Anorexia/Cachexia:** Weight, appetite, nutritional status, body mass index.
* **General:** Blood pressure, signs and symptoms of thromboembolic events (e.g., leg pain or swelling, shortness of breath, chest pain), glucose levels (especially in diabetic patients), adrenal function (particularly with prolonged use or discontinuation), and potential vision changes.
## Clinical Pearls
* The liquid formulation contains significant calories and sugar; consider when managing diabetic patients or those on fluid restrictions.
* Due to the risk of adrenal insufficiency, abrupt discontinuation should be avoided, especially after prolonged use. Tapering may be considered.
* Thromboembolic events are a serious risk; patients should be advised to report any signs or symptoms immediately.
* Onset of appetite stimulation and weight gain may take several weeks.
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*This information is intended for healthcare professionals. Please verify current prescribing information with the official drug label or other authoritative sources before making clinical decisions.*
