Does Tamsulosin (Flomax) cause constipation?

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Last updated: April 28, 2025View editorial policy

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From the FDA Drug Label

In an open-label, 12-month safety study, 87 patients were treated with tamsulosin hydrochloride. The most frequently reported adverse events (<5%) from the pooled data of both studies were urinary tract infection, vomiting, pyrexia, headache, nasopharyngitis, cough, pharyngitis, influenza, diarrhea, abdominal pain, and constipation.

Constipation is a possible side effect of Flomax (tamsulosin), as reported in the drug label 1.

  • Key points:
    • Constipation was reported as an adverse event in a safety study.
    • The frequency of constipation was less than 5%.
  • Clinical decision: Patients taking Flomax should be monitored for constipation, especially if they have a history of gastrointestinal problems.

From the Research

Flomax (tamsulosin) can cause constipation as a side effect, though it's not among the most common side effects reported, with an incidence of approximately 1-5% of patients taking this medication. Flomax is an alpha-blocker primarily used to treat benign prostatic hyperplasia (BPH) by relaxing muscles in the prostate and bladder neck, which improves urinary flow. The constipation side effect occurs because alpha-blockers can affect smooth muscle function throughout the body, including the intestines, potentially slowing gut motility in some patients 2.

Management of Constipation

If you experience constipation while taking Flomax, several strategies may help alleviate this symptom:

  • Staying well-hydrated
  • Increasing dietary fiber
  • Regular physical activity For persistent constipation, it is recommended to speak with your healthcare provider, who might recommend:
  • Stool softeners
  • Other interventions
  • Possibly adjust your medication regimen

Importance of Medical Consultation

Never discontinue Flomax without medical consultation, as the benefits for treating BPH typically outweigh this potential side effect for most patients 3, 4. The efficacy and safety of alpha-1 blockers, including tamsulosin, have been extensively studied, and they are generally well-tolerated, with doxazosin and tamsulosin seeming to be more effective than other alpha-1 blockers 2.

Key Considerations

When considering the use of Flomax, it is essential to weigh the potential benefits against the possible side effects, including constipation. Given the relatively low incidence of constipation and the effectiveness of Flomax in treating BPH, the benefits of using Flomax often outweigh the risks for most patients 5, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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