Megace (Megestrol Acetate)

Megestrol acetate is used as an appetite stimulant and antineoplastic agent in several oncologic and wasting conditions.

• Cancer‑related cachexia: improves appetite and promotes weight gain in patients with advanced malignancy.
• Advanced breast cancer: provides hormonal therapy to slow tumor progression in hormone‑responsive disease.
• Endometrial carcinoma: used as a hormonal treatment option for certain stages of endometrial cancer.

• Megestrol acetate is a synthetic progestogen that binds to intracellular progesterone receptors, modulating gene transcription. Its glucocorticoid‑like activity influences metabolic pathways, leading to increased appetite and weight gain. In hormone‑sensitive tumors, the drug exerts antineoplastic effects by antagonizing estrogen‑driven proliferation and inducing cell‑cycle arrest. Additionally, it reduces circulating cortisol levels and may alter cytokine production, contributing to its clinical effects.

Megestrol acetate may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Weight gain: increased appetite leading to excess weight.
• Edema: peripheral swelling, especially in lower limbs.
• Fatigue: generalized tiredness.
• Hot flashes: transient vasomotor symptoms.
• Alopecia: thinning of scalp hair.

Serious or Rare Side Effects

• Thromboembolic events: deep vein thrombosis or pulmonary embolism.
• Adrenal insufficiency: signs of cortisol deficiency.
• Severe infection: opportunistic or bacterial infections.
• Cushingoid syndrome: hypercortisolism‑like features.
• Hyperglycemia: elevated blood glucose levels.
• Hepatotoxicity: abnormal liver enzymes or liver injury.

When prescribing megestrol acetate, clinicians should consider several safety precautions.

• Monitor blood glucose: hyperglycemia may develop, especially in diabetic patients.
• Assess thromboembolic risk: evaluate history of clotting disorders before initiating therapy.
• Evaluate liver function: periodic liver enzyme tests are recommended.
• Use caution in hormone‑sensitive tumors: may affect disease progression.
• Avoid use in pregnancy: potential fetal risk, contraindicated when possible.
• Store at ambient temperature: keep in original packaging, protect from moisture and direct sunlight.

Megestrol acetate can interact with other medicines, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): increase megestrol levels and risk of toxicity.
• Anticoagulants (e.g., warfarin): enhanced anticoagulant effect may raise bleeding risk.
• Insulin or oral hypoglycemics: potentiated hypoglycemic effect, requiring dose adjustment.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce drug exposure and effectiveness.
• Oral contraceptives: decreased hormonal efficacy, consider alternative contraception.
• NSAIDs: combined use may increase gastrointestinal irritation.