Megace (Megestrol Acetate)

Megestrol acetate is used as an appetite stimulant and antineoplastic agent in several disease states.

• Cachexia (AIDS or cancer): Improves appetite and promotes weight gain in affected patients.
• Advanced breast cancer: Provides hormonal control to slow disease progression.
• Endometrial carcinoma: Acts as a progestogenic therapy for tumor management.

• Megestrol acetate binds to progesterone receptors, acting as an agonist that modulates gene transcription involved in metabolic and proliferative pathways. Its glucocorticoid‑like activity enhances appetite by influencing hypothalamic centers and contributes to antineoplastic effects through inhibition of tumor cell growth and induction of apoptosis in hormone‑sensitive cancers.

Megestrol acetate may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Weight gain: Increased adipose tissue and fluid retention.
• Edema: Peripheral swelling, especially in the lower extremities.
• Hypertension: Elevated blood pressure requiring monitoring.
• Hyperglycemia: Raised blood glucose levels, may affect diabetic patients.
• Nausea: Gastrointestinal discomfort and occasional vomiting.
• Fatigue: Generalized tiredness and reduced stamina.

Serious or Rare Side Effects

• Thromboembolic events: Deep vein thrombosis or pulmonary embolism.
• Adrenal insufficiency: Suppression of endogenous cortisol production.
• Severe infection: Increased susceptibility due to immunomodulation.
• Hepatic dysfunction: Elevated liver enzymes or hepatitis.
• Cushingoid appearance: Moon face, central obesity, skin changes.
• Acute pancreatitis: Inflammation of the pancreas presenting with abdominal pain.

Before initiating therapy, clinicians should evaluate patient‑specific risk factors and monitor relevant clinical parameters.

• Blood glucose monitoring: Check fasting glucose and HbA1c regularly.
• Blood pressure assessment: Measure BP at baseline and periodically.
• Thromboembolic risk: Assess history of clotting disorders and consider prophylaxis.
• Adrenal function: Evaluate cortisol levels if long‑term therapy is planned.
• Concomitant glucocorticoids: Adjust doses to avoid additive steroid effects.
• Store at room temperature: Keep in the original container, protect from moisture and direct sunlight.

Megestrol acetate can alter the pharmacokinetics or pharmacodynamics of several co‑administered medicines.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole): May increase megesterol levels and toxicity.
• Anticoagulants (e.g., warfarin): Enhanced anticoagulant effect, risk of bleeding.
• Insulin or oral hypoglycemics: Potentiated hypoglycaemic effect, require dose adjustment.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): May reduce therapeutic efficacy.
• Oral contraceptives: Decreased hormonal contraceptive effectiveness.
• NSAIDs: Increased risk of gastrointestinal irritation and edema.