Can Flomax (tamsulosin) be used to treat overactive bladder in females?

Tamsulosin (Flomax) Is Not Recommended for Treating Overactive Bladder in Females

Tamsulosin (Flomax) is not recommended for treating overactive bladder in females as it lacks efficacy for this indication and is specifically approved only for benign prostatic hyperplasia in males.

Evidence Against Using Tamsulosin for Overactive Bladder in Females

FDA Labeling and Indications

• The FDA drug label clearly states that tamsulosin is specifically indicated for "treatment of signs and symptoms of benign prostatic hyperplasia (BPH)" 1
• The drug label explicitly states "Tamsulosin Hydrochloride Capsules is not for women" 1
• Tamsulosin is not approved for use in females of any age for any indication 1

Clinical Trial Evidence

• A randomized, double-blind, placebo-controlled multicenter study specifically investigating tamsulosin in women with overactive bladder found that tamsulosin OCAS (Oral Controlled Absorption System) was not effective for treating OAB in women 2
• This study tested multiple doses of tamsulosin (0.25,0.5,1.0, and 1.5 mg) against tolterodine and placebo, finding no statistically significant difference between tamsulosin and placebo for:
  • Mean number of voids per 24 hours (primary endpoint)
  • Mean voided volume per void
  • Incontinence episodes
  • Urgency episodes
  • Quality of life scores 2

Recommended Treatments for Overactive Bladder in Females

First-Line Therapies

• Anticholinergic medications (muscarinic receptor antagonists) such as:
  • Tolterodine
  • Solifenacin
  • Oxybutynin

Second-Line Therapies

• Beta-3 adrenergic receptor agonists:
  • Mirabegron has demonstrated efficacy and safety for overactive bladder symptoms 3

Mechanism of Action and Rationale

Tamsulosin is an alpha-1 adrenergic receptor blocker that works primarily by relaxing smooth muscle in the prostate and bladder neck, which helps relieve urinary obstruction in men with BPH 1. This mechanism is specifically targeted at male anatomy and the pathophysiology of BPH.

In contrast, overactive bladder in females is primarily related to detrusor muscle overactivity, which is better addressed by:

• Anticholinergics that block muscarinic receptors in the bladder, reducing involuntary detrusor contractions
• Beta-3 agonists that stimulate beta-3 adrenergic receptors in the detrusor muscle, promoting relaxation during the storage phase

Safety Considerations

While tamsulosin was generally well-tolerated in women in the clinical trial (with only 4.7% discontinuing due to adverse events) 2, using medications outside their approved indications should be avoided when:

1. Evidence shows lack of efficacy for the intended use
2. Better alternatives with proven efficacy exist
3. The medication is explicitly labeled as not for use in the specific population

Conclusion

Based on the available evidence, tamsulosin should not be used to treat overactive bladder in females. The European Association of Urology guidelines and clinical trial evidence support the use of anticholinergics and beta-3 agonists as the appropriate pharmacological treatments for overactive bladder in women, while tamsulosin has been specifically studied and found ineffective for this indication.