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# Megestrol Acetate
## Overview
Megestrol acetate is a synthetic progestin with antineoplastic and antiestrogenic properties. It is available in oral suspension and tablet formulations.
## Primary Indications
* **Cachexia, anorexia, or unexplained significant weight loss:** Associated with conditions such as acquired immunodeficiency syndrome (AIDS) or cancer.
* **Palliative treatment of advanced or metastatic breast cancer:** Particularly in postmenopausal women.
* **Palliative treatment of advanced or metastatic endometrial cancer.**
## Adult Dosing
* **Weight Loss/Cachexia:**
* Initial: 800 mg (20 mL) orally once daily.
* Some patients may respond to lower doses (e.g., 400 mg daily).
* Continue treatment as long as the patient is benefiting.
* **Breast Cancer:**
* 40 mg (10 mL) orally 4 times daily (total 160 mg daily).
* Alternatively, 400-800 mg orally once daily.
* **Endometrial Cancer:**
* 40 mg (10 mL) orally 4 times daily (total 160 mg daily).
## Pediatric Dosing
There is no established pediatric dosing for megestrol acetate.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are typically recommended, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustments are typically recommended, but caution is advised.
## Contraindications
* Known hypersensitivity to megestrol acetate or any component of the formulation.
* Pregnancy: Megestrol acetate is contraindicated in pregnancy due to potential fetal harm.
* Undiagnosed abnormal vaginal bleeding.
## Adverse Effects
* **Common:** Weight gain, increased appetite, hot flashes, hypertension, dyspnea, rash, nausea, diarrhea, abdominal pain, sexual dysfunction.
* **Serious:** Thromboembolic events (e.g., deep vein thrombosis, pulmonary embolism), adrenal insufficiency (especially with prolonged use or abrupt discontinuation), hyperglycemia, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Endocrine:** Menstrual irregularities, vaginal bleeding, breast tenderness, galactorrhea.
## Key Drug Interactions
* **CYP3A4 Inhibitors/Inducers:** May alter megestrol acetate concentrations. Caution is advised when used with strong inhibitors or inducers of CYP3A4.
* **Antidiabetic Agents:** Megestrol acetate can cause hyperglycemia; patients on antidiabetic medications may require dose adjustments.
## Monitoring
* **Weight and appetite:** Especially in patients treated for cachexia.
* **Blood pressure:** Monitor for hypertension.
* **Signs of thromboembolic events:** Leg pain/swelling, shortness of breath, chest pain.
* **Adrenal function:** Especially with prolonged use or during periods of stress or illness, or if abrupt discontinuation is considered.
* **Blood glucose:** In diabetic patients.
* **Tumor response:** In patients with advanced cancer.
## Clinical Pearls
* Megestrol acetate should not be used during pregnancy. Advise patients of reproductive potential to use effective contraception.
* Gradual withdrawal of the drug is recommended, especially after prolonged therapy, to minimize the risk of adrenal insufficiency.
* The oral suspension contains sucrose; caution in diabetic patients.
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***Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature for complete details before making clinical decisions. This information may not be exhaustive and does not replace professional judgment.*
