Oxybutynin Treatment for Urinary Incontinence in Men with BPH
For men with BPH already on an alpha-blocker who have persistent storage symptoms (urgency, frequency), adding an anticholinergic medication like oxybutynin is appropriate, but only after confirming post-void residual (PVR) is less than 150 mL. 1
Treatment Algorithm for Persistent Storage Symptoms
Step 1: Verify Alpha-Blocker Optimization
- Ensure the patient has been on alpha-blocker therapy for at least 4-12 weeks, as this is the timeframe needed to assess adequate response 1
- Confirm the patient is on an appropriate dose of alpha-blocker (tamsulosin, alfuzosin, or silodosin) 2
Step 2: Measure Post-Void Residual
- Obtain a PVR measurement before initiating any anticholinergic therapy 1, 3
- Do not use anticholinergics if PVR >150 mL due to increased risk of urinary retention 1
- This is a critical safety measure that cannot be skipped 1
Step 3: Add Anticholinergic Therapy
Recommended anticholinergic options for combination with alpha-blockers include: 4
- Oxybutynin (immediate or extended-release formulation) 4, 5
- Solifenacin 1, 6
- Tolterodine 1
- Darifenacin 4
- Trospium 4
The 2023 European Association of Urology guidelines specifically support combination therapy with alpha-blockers plus antimuscarinics for men with moderate-to-severe storage LUTS, showing superiority over alpha-blockers alone in reducing urgency, urgency incontinence, voiding frequency, and nocturia 1
Step 4: Alternative to Anticholinergics
If anticholinergics are contraindicated or not tolerated, consider mirabegron (beta-3 agonist):
- Mirabegron 25-50 mg daily in combination with tamsulosin has demonstrated efficacy for persistent storage symptoms 1, 7
- Lower risk of urinary retention compared to anticholinergics, with estimated AUR incidence of 1.7% 1
- Particularly useful in patients with cognitive concerns or dry mouth intolerance 4
Evidence Supporting Combination Therapy
Multiple randomized controlled trials demonstrate that alpha-blocker plus anticholinergic combination therapy is superior to monotherapy:
- The NEPTUNE trial showed combination solifenacin plus tamsulosin significantly improved storage symptoms 1
- Meta-analysis confirmed combination treatment does not adversely affect voiding function parameters when PVR is appropriately monitored 1
- Extended-release oxybutynin combined with tamsulosin showed efficacy and safety in a randomized, double-blind, placebo-controlled study 1
Critical Safety Considerations
Absolute Contraindications to Anticholinergics
- Narrow-angle glaucoma (unless approved by ophthalmologist) 4, 5
- Impaired gastric emptying 4, 5
- History of urinary retention 4, 5
- PVR >150 mL 1
Monitoring Requirements
- Measure PVR before initiating therapy and monitor during treatment 1
- Re-evaluate at 4-12 weeks after starting combination therapy using IPSS scoring 1
- Most trials were short duration (6-12 weeks) and included only men with low baseline PVR volumes 3
Common Adverse Effects
- Dry mouth (most common) 5
- Constipation 5
- Blurred vision 5
- Cognitive impairment (use caution in elderly) 4, 5
- Small increases in PVR may occur but acute urinary retention rates remain low when patients are appropriately selected 3
Common Pitfalls to Avoid
Do not skip PVR measurement - This is the single most important safety measure before adding anticholinergic therapy 1, 3
Do not use anticholinergics as monotherapy in men with BPH - Always ensure alpha-blocker therapy is optimized first 1, 4
Do not combine low-dose tadalafil (5 mg) with alpha-blockers - This combination offers no advantage over either agent alone and increases side effects 1
Do not ignore prostate size - If prostate volume is >30 cc or PSA >1.5 ng/mL, consider adding a 5-alpha reductase inhibitor rather than just an anticholinergic 1, 4
When to Refer
Refer to urology if: 1
- Failure to respond to combination medical therapy
- Recurrent urinary retention
- Persistent hematuria
- Recurrent urinary tract infections
- Rising PSA on therapy
- Renal insufficiency