Can Tamsulosin (alpha-blocker) cause gynaecomastia?

Tamsulosin and Gynecomastia

Tamsulosin can cause gynecomastia, as evidenced by case reports from the Italian spontaneous reporting system and the WHO database showing a significant association between tamsulosin use and gynecomastia development. 1

Mechanism and Evidence

Tamsulosin is an α1-adrenergic receptor antagonist (α1-ARA) commonly used to treat benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). The association between tamsulosin and gynecomastia has been documented in pharmacovigilance databases:

• Analysis of the Italian spontaneous reporting system found 10 cases of gynecomastia associated with tamsulosin, with a Reporting Odds Ratio (ROR) of 5.3 (95% CI 1.8,15.7) 1
• The WHO database (VigiBase™) contained 84 reports of gynecomastia with tamsulosin as the suspected drug, showing the highest Information Component value within this class of drugs 1

While the exact mechanism is not fully elucidated, it may involve hormonal imbalance at the breast tissue level, similar to other medications known to cause gynecomastia.

Risk Assessment

The risk of gynecomastia with tamsulosin appears to be relatively uncommon compared to other medications known to cause this side effect, such as:

• Spironolactone (well-documented to cause gynecomastia) 2
• 5-α reductase inhibitors like finasteride and dutasteride 2
• Antipsychotics that cause hyperprolactinemia 2

Management Algorithm

When gynecomastia develops in a patient taking tamsulosin:

1. Confirm true gynecomastia: Distinguish between true glandular breast tissue enlargement versus pseudogynecomastia (fatty tissue deposition) 2

2. Evaluate severity and impact:

   • Presence of mastodynia (breast pain/tenderness)
   • Size of breast enlargement
   • Duration of gynecomastia
   • Psychological impact on the patient

3. Consider medication change:

   • If clinically appropriate, consider switching to another α1-ARA with potentially lower risk of gynecomastia (such as alfuzosin, doxazosin, or silodosin) 1
   • Consider alternative medication classes for BPH/LUTS if appropriate

4. Treatment options for established gynecomastia:

   • For painful gynecomastia or cases with psychological impact, tamoxifen 20 mg/day may be effective 3
     • More effective for smaller gynecomastias (<4 cm diameter) 3
     • Less effective for gynecomastia lasting >2 years 3
   • For long-standing gynecomastia (>12-24 months) not responding to medication changes, surgical options may be considered 2

Important Clinical Considerations

• Gynecomastia may present as an acute syndrome characterized by unilateral or bilateral painful/tender breast enlargement that often resolves spontaneously over time 4

• The response to treatment depends on:

  • Size of gynecomastia (smaller lesions respond better) 3
  • Duration (more recent cases respond better) 3

• Regular monitoring is recommended for patients on tamsulosin who develop gynecomastia, as some cases may resolve spontaneously with continued treatment 4

• Document and report cases of tamsulosin-associated gynecomastia to contribute to pharmacovigilance databases, as this association is relatively newly recognized 1

While gynecomastia can be distressing for patients, it is generally not associated with serious long-term health consequences when related to medication use, and appropriate management can significantly improve quality of life.