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# Megestrol Acetate (Megestrol)
## Overview
Megestrol acetate is a synthetic progestin.
## Primary Indications
* **Cachexia, anorexia, or unexplained weight loss:** Associated with conditions such as acquired immunodeficiency syndrome (AIDS) or cancer.
* **Palliative treatment of advanced breast cancer** (historically).
* **Endometrial carcinoma** (historically).
## Adult Dosing
* **For cachexia/anorexia/weight loss:**
* Oral suspension: Typically 625 mg orally once daily. Doses can range from 125 mg to 800 mg daily, depending on patient response and tolerability.
* Oral tablets: Can be used at similar dosages.
* **For palliative treatment of advanced breast cancer or endometrial carcinoma:** Historically, doses of 40 mg orally four times daily (160 mg/day) or 40-80 mg orally once daily were used. Current use for these indications is less common.
## Pediatric Dosing
There is no established pediatric dosing for megestrol acetate. Use in pediatric populations is generally not recommended due to lack of data and potential risks.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are established.
* **Hepatic Impairment:** No specific dose adjustments are established. Caution is advised as the drug is metabolized in the liver.
## Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy: Megestrol acetate is contraindicated in pregnancy due to potential for fetal harm.
## Adverse Effects
* **Common:** Weight gain, increased appetite, hot flashes, hypertension, dyspnea, nausea, diarrhea, edema, abdominal pain, headache, rash.
* **Serious:** Thrombophlebitis, pulmonary embolism, cerebrovascular accident (stroke), myocardial infarction, adrenal insufficiency, hyperglycemia, new-onset diabetes, exacerbation of existing diabetes, opportunistic infections (in HIV-infected patients).
## Key Drug Interactions
* **CYP3A4 Inhibitors/Inducers:** May alter megestrol acetate pharmacokinetics, though clinical significance is often unclear. Examples include ritonavir, indinavir, nelfinavir, ketoconazole, itraconazole, rifampin, phenytoin.
* **Aminoglutethimide:** May decrease plasma concentrations of megestrol acetate.
## Monitoring
* Weight and appetite changes.
* Blood pressure.
* Blood glucose levels, particularly in patients with diabetes or risk factors for diabetes.
* Signs of thromboembolic events (e.g., leg pain, swelling, shortness of breath, chest pain).
* Adrenal function if prolonged use or abrupt discontinuation is suspected.
* Pregnancy status in women of childbearing potential.
## Clinical Pearls
* Megestrol acetate is primarily used for its appetite-stimulating effects in the context of significant weight loss.
* Onset of effect may take several weeks.
* Due to potential adrenal suppression, abrupt discontinuation should be avoided, especially after prolonged high-dose therapy. Tapering may be necessary.
* Risk of thromboembolic events, although the incidence may be lower than with other progestins.
* Women of childbearing potential should use effective non-hormonal contraception during treatment.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional guidelines before making clinical decisions.
