How does tadalafil (Cialis) help with urinary retention in patients with benign prostatic hyperplasia (BPH)?

How Tadalafil Helps with Urinary Retention in BPH

Direct Answer

Tadalafil does NOT help with acute urinary retention and should not be used for this indication. For acute urinary retention due to BPH, alpha blockers (tamsulosin or alfuzosin) are the recommended first-line treatment, not tadalafil 1, 2.

Mechanism of Action for LUTS/BPH (Not Retention)

Tadalafil 5 mg daily is FDA-approved and guideline-recommended for lower urinary tract symptoms (LUTS) due to BPH, but this is fundamentally different from treating urinary retention 3, 4. The mechanism involves:

• Smooth muscle relaxation in the prostate, bladder neck, urethra, and bladder through phosphodiesterase-5 inhibition, which increases cyclic GMP levels 5
• Improved bladder blood flow and endothelial function, with demonstrated improvements in vascular elasticity (brachial-ankle pulse wave velocity) after 3-12 months of treatment 5
• Reduction in bladder overactivity and irritative symptoms (frequency, urgency, nocturia) through effects on bladder smooth muscle 3, 4

Clinical Evidence for LUTS (Not Retention)

Efficacy for Lower Urinary Tract Symptoms

• Tadalafil 5 mg daily produces a mean IPSS reduction of -5.4 to -5.6 points compared to -3.6 points with placebo, representing a clinically meaningful difference of approximately 1.7-2.0 points 3, 4, 6
• Symptom improvement begins as early as 1 week, with statistical significance achieved by week 4 7, 6
• Approximately 69% of patients achieve clinically meaningful improvement (≥3-point IPSS reduction) by study endpoint 7

Limited Effect on Urinary Flow

• Tadalafil produces only a small, statistically significant increase in maximum urinary flow rate (Qmax) of 1.1 mL/sec versus 0.4 mL/sec for placebo—a difference of only 0.7 mL/sec 4, 8
• This minimal flow improvement explains why tadalafil is ineffective for acute urinary retention, which requires substantial improvement in bladder outlet obstruction 4, 8

Evidence Against Use in Acute Urinary Retention

Failed Clinical Trial

• A 2018 randomized controlled trial specifically tested tadalafil 10 mg plus tamsulosin versus tamsulosin alone for acute urinary retention in 80 BPH patients 9
• Results showed no significant benefit: 65% voiding success with combination therapy versus 72.5% with tamsulosin alone at 1 week (p=0.469) 9
• This demonstrates that adding tadalafil to alpha blockers provides no advantage for acute retention 9

Guideline Recommendations for Acute Retention

The correct treatment algorithm for acute urinary retention due to BPH is:

1. Immediate urethral catheterization for bladder decompression 2
2. Start an alpha blocker (tamsulosin 0.4 mg or alfuzosin 10 mg)—these require no dose titration 2
3. Continue alpha blocker for at least 3 days before attempting catheter removal 1, 2
4. Attempt trial without catheter (TWOC) after 3+ days of therapy 1, 2
5. Expected success rates: 60% with alfuzosin, 47% with tamsulosin, versus 29-39% with placebo 1, 2

When Tadalafil IS Appropriate

Indications for Tadalafil 5 mg Daily

• Moderate to severe LUTS/BPH (IPSS ≥13) in men who have NOT progressed to acute urinary retention 3, 4
• Combination of LUTS/BPH and erectile dysfunction—tadalafil treats both conditions simultaneously 3, 4
• Alternative to alpha blockers in patients who cannot tolerate or have contraindications to alpha blockers 3

Important Contraindications and Warnings

• Absolute contraindication: Concomitant nitrate use (risk of severe hypotension) 3
• Do NOT combine tadalafil 5 mg with alpha blockers—this combination offers no additional symptom benefit over either agent alone and increases side effects 1, 3
• Common adverse effects: Headache, flushing, rhinitis, dyspepsia 3
• Cardiovascular assessment should be performed before prescribing 3

Key Clinical Pitfalls

• Do not confuse LUTS/BPH with acute urinary retention—these are different clinical entities requiring different treatments 1, 2
• Do not use tadalafil for acute retention—alpha blockers are the evidence-based choice 1, 2, 9
• Do not combine tadalafil with alpha blockers—this increases side effects without improving outcomes 1, 3
• Patients who successfully void after acute retention remain at high risk for recurrent retention and should continue alpha blocker therapy long-term 1, 2