Nebido (Testosterone Undecanoate)

• Nebido (testosterone undecanoate) acts on the androgen pathway to replace deficient testosterone in men.
• Male hypogonadism: restores normal testosterone concentrations and alleviates related symptoms.
• Testosterone replacement therapy: maintains physiological hormone levels in men with documented deficiency.
• Secondary hypogonadism: supports endogenous hormone production when pituitary or hypothalamic dysfunction reduces testosterone output.

• Testosterone undecanoate is a long‑acting ester of testosterone that, after intramuscular administration, is hydrolyzed to native testosterone. The liberated hormone binds intracellular androgen receptors, modulating gene transcription that promotes anabolic protein synthesis and suppresses catabolic pathways. This restores androgenic activity, supporting the development and maintenance of male secondary sexual characteristics, libido, muscle mass, and erythropoiesis. It also influences the hypothalamic‑pituitary‑gonadal axis, providing feedback that regulates endogenous hormone production.

Nebido may be associated with a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Injection site pain: mild to moderate discomfort at the injection site.
• Acne: increased sebaceous gland activity leading to skin eruptions.
• Increased hematocrit: rise in red blood cell concentration.

Serious or Rare Side Effects

• Erythrocytosis: excessive increase in red blood cells that may raise thrombosis risk.
• Cardiovascular events: potential for myocardial infarction or stroke.
• Severe allergic reaction: anaphylaxis or angioedema requiring immediate medical attention.

• When using Nebido, several precautions should be observed to ensure patient safety.
• Monitor hematocrit: regular blood count checks to detect erythrocytosis.
• Assess cardiovascular risk: evaluate history of heart disease before initiating therapy.
• Screen for prostate disease: perform PSA testing and digital rectal exam.
• Avoid use in known hypersensitivity: discontinue if allergic reaction occurs.
• Pregnancy and breastfeeding: not indicated for women; avoid exposure.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Nebido can interact with other medicines, requiring careful management.

Major Interactions (Avoid)

• Warfarin: may potentiate anticoagulant effect and increase bleeding risk.
• Insulin: may alter glucose control, requiring dose adjustments.
• CYP3A4 inhibitors: may raise testosterone levels and increase adverse effect potential.

Moderate Interactions (Monitor Closely)

• Antihypertensives: may enhance blood pressure‑lowering effect.
• Glucocorticoids: may exacerbate fluid retention.
• Estrogen therapy: may counteract androgenic actions.