Megestat (Megestrol Acetate)

Megestat is a synthetic progestogen used in oncology and supportive care to address conditions that cause severe weight loss or hormone‑driven tumor growth.

• Cancer‑related cachexia or AIDS‑associated weight loss: helps increase appetite and promote weight gain.
• Advanced breast cancer: provides antineoplastic activity by modulating progesterone receptors.
• Endometrial cancer: used as part of hormonal therapy to inhibit tumor progression.

• Megestrol acetate acts as a synthetic progestogen that binds to progesterone receptors, influencing gene transcription involved in appetite regulation and cell proliferation. Its glucocorticoid‑like activity also contributes to increased food intake and exerts antineoplastic effects by altering hormone‑dependent tumor pathways.

Megestat may cause a range of adverse reactions, ranging from mild to serious.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Weight gain: due to increased appetite and fluid retention.
• Edema: peripheral swelling, especially in lower extremities.
• Fatigue: general tiredness or reduced energy.
• Hot flashes: transient warmth and sweating.
• Mood changes: irritability or mild depression.

Serious or Rare Side Effects

• Thromboembolic events: deep vein thrombosis or pulmonary embolism.
• Hyperglycemia: elevated blood glucose, may worsen diabetes.
• Cushingoid features: facial rounding, central obesity.
• Severe infection: increased susceptibility due to immunosuppression.
• Adrenal suppression: reduced endogenous cortisol production.
• Hepatotoxicity: abnormal liver enzymes or liver injury.

Before initiating Megestat, clinicians should evaluate patient‑specific risk factors and monitor for potential complications.

• Blood glucose monitoring: assess for hyperglycemia, especially in diabetic patients.
• Thromboembolic risk assessment: evaluate history of clotting disorders.
• Adrenal function: consider baseline cortisol levels and taper if discontinued.
• Hormone‑sensitive tumors: use caution in cancers responsive to progesterone.
• Pregnancy and lactation: avoid use due to unknown safety profile.
• Store at ambient temperature: keep in original packaging, protect from moisture and direct sunlight.

Megestat can interact with several medication classes, requiring careful management.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase Megestat exposure.
• Anticoagulants (e.g., warfarin): heightened risk of thrombosis.
• Insulin or oral hypoglycemics: enhanced glucose‑lowering effect, risk of hypoglycemia.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, phenytoin): may reduce therapeutic levels.
• Other corticosteroids: additive glucocorticoid effects.
• Hormonal therapies (e.g., tamoxifen): potential antagonism of anti‑cancer activity.