Megesin (Megestrol Acetate)

Megestrol acetate is indicated for conditions where appetite stimulation or antineoplastic activity is required.

• Cachexia associated with AIDS: improves appetite and promotes weight gain in patients with AIDS‑related wasting.
• Cachexia associated with cancer: helps increase caloric intake and stabilizes body weight in oncology patients.
• Hormone‑responsive breast cancer: provides antineoplastic effects by inhibiting tumor growth in estrogen‑sensitive disease.
• Endometrial cancer: used as hormonal therapy to control disease progression in progesterone‑responsive tumors.

• Megestrol acetate is a synthetic progestogen that binds to intracellular progesterone receptors, modulating gene transcription. Its progestogenic activity exerts antineoplastic effects in hormone‑sensitive tumors, while glucocorticoid‑like actions on the hypothalamic‑pituitary‑adrenal axis reduce catabolism and stimulate appetite, leading to weight gain.

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

Common Side Effects

• Nausea: mild gastrointestinal upset.
• Vomiting: occasional emesis.
• Edema: peripheral swelling, often in lower limbs.
• Fatigue: generalized tiredness.
• Weight gain: excessive increase beyond therapeutic goal.
• Hot flashes: transient warmth sensations.

Serious or Rare Side Effects

• Thromboembolic events: deep vein thrombosis or pulmonary embolism.
• Adrenal suppression: reduced cortisol production.
• Hyperglycemia: elevated blood glucose levels.
• Hepatotoxicity: liver enzyme abnormalities.
• Severe allergic reaction: rash, angioedema, or anaphylaxis.

Before prescribing Megestrol acetate, clinicians should consider several safety measures.

• Pregnancy: contraindicated (Category X) due to risk of fetal malformations.
• Breastfeeding: not recommended; drug may pass into milk and affect the infant.
• Diabetes: monitor blood glucose as the drug can raise glucose levels.
• Thrombotic risk: assess for history of clotting disorders before use.
• Liver disease: use with caution; hepatic impairment may increase exposure.
• Store at ambient temperature: keep below 25 °C, protect from moisture and light in the original packaging.

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

Major Interactions (Avoid)

• Anticoagulants (e.g., warfarin): increased risk of thrombosis.
• CYP3A4 inducers (e.g., rifampin): may reduce megesterol levels and effectiveness.
• Glucocorticoids: additive effects on glucose metabolism and immunosuppression.

Moderate Interactions (Monitor Closely)

• Antidiabetic agents: potential for hyperglycemia, requiring dose adjustments.
• Hormonal therapies (e.g., tamoxifen): may interfere with hormonal balance.
• CYP3A4 inhibitors (e.g., ketoconazole): could increase megesterol exposure.