Megesin (Megestrol Acetate)

Megesin (megestrol acetate) acts as a progestogenic agent that influences metabolic and hormonal pathways associated with weight loss and hormone‑sensitive cancers.

• Cachexia associated with AIDS or cancer: improves appetite and promotes weight gain in affected patients.
• Anorexia and weight loss: increases food intake and helps restore body mass.
• Hormone‑responsive cancers such as endometrial or breast cancer: provides antigonadotropic effects that can slow tumor progression.

• Megestrol acetate is a synthetic progestin that binds with high affinity to intracellular progesterone receptors. Activation of these receptors produces antigonadotropic effects, reducing circulating gonadotropins and estrogen levels, and modulates hypothalamic pathways that increase appetite. The drug also influences glucocorticoid receptors, contributing to fluid retention and metabolic changes that support weight gain. Additionally, it may alter cytokine production, further aiding in the reversal of catabolic states.

Megestrol acetate may be associated with a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Weight gain: excess increase in body weight.
• Increased appetite: heightened desire for food.
• Nausea: occasional stomach upset.
• Edema: mild fluid retention, especially in the lower limbs.

Serious or Rare Side Effects

• Thromboembolic events: deep vein thrombosis or pulmonary embolism.
• Hyperglycemia: significant rise in blood glucose levels.
• Adrenal insufficiency: reduced cortisol production.
• Hepatic dysfunction: elevated liver enzymes or hepatitis.

When prescribing Megesin, clinicians should consider several safety measures to minimize risks.

• Monitor blood glucose: check fasting and post‑prandial levels regularly.
• Assess thromboembolic risk: evaluate history of clotting disorders before initiation.
• Observe blood pressure: watch for hypertension, especially in patients with cardiovascular disease.
• Evaluate adrenal function: consider cortisol testing if long‑term therapy is planned.
• Use caution in pregnancy: potential fetal effects are not well established; avoid unless benefits outweigh risks.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Megestrol acetate can alter the activity of several concomitant medicines, requiring attention to interaction potential.

Major Interactions (Avoid)

• CYP3A4 inducers (e.g., rifampin, phenytoin): may markedly reduce megestrol exposure.
• Anticoagulants (warfarin): increased risk of thrombosis may counteract anticoagulant effect.
• Antifungal agents (ketoconazole, itraconazole): can raise megestrol levels and increase toxicity.

Moderate Interactions (Monitor Closely)

• Corticosteroids: additive fluid retention and metabolic effects.
• Insulin or oral hypoglycemics: may exacerbate hyperglycemia, requiring closer monitoring.
• Other hormonal therapies (tamoxifen, aromatase inhibitors): could interfere with endocrine balance.