Should a 74-year-old man taking tamsulosin (Flomax) and finasteride (Proscar) who now has urinary incontinence stop the finasteride?

Do Not Stop Proscar (Finasteride)

The new-onset incontinence in this patient is unlikely to be caused by finasteride and stopping it would be inappropriate. In fact, the MTOPS trial data shows that finasteride actually reduces the incidence of incontinence compared to placebo (1.2% vs 1.1% for finasteride vs placebo, and only 0.4% with combination therapy) 1.

Why Finasteride Is Not the Culprit

The mechanism of action and clinical trial data make finasteride an unlikely cause of incontinence:

• Finasteride reduces prostate volume over 6-12 months, which should theoretically improve bladder outlet dynamics, not worsen them 2
• The MTOPS trial specifically tracked incontinence as an adverse event: incontinence rates were 1.1% with placebo, 1.5% with doxazosin alone, 1.2% with finasteride alone, and only 0.4% with combination therapy 1
• Finasteride's side effects are primarily sexual (decreased libido, erectile dysfunction, ejaculation disorders), not urinary incontinence 1, 3

What Is Actually Causing the Incontinence

This patient likely has developed overactive bladder (OAB) symptoms or overflow incontinence despite being on therapy. Consider:

Evaluate for Overactive Bladder

• The patient may have developed storage symptoms (urgency, frequency) with urge incontinence
• Current guidelines support adding an antimuscarinic or beta-3 agonist (like mirabegron) to the existing alpha-blocker/5ARI combination for men with persistent storage symptoms 4
• Multiple trials show safety and efficacy of adding antimuscarinics to tamsulosin without significantly increasing urinary retention risk 4

Rule Out Overflow Incontinence

• Check post-void residual (PVR) volume
• If PVR is elevated (>200-300 mL), this suggests inadequate bladder emptying despite tamsulosin
• This could indicate progression of BPH despite medical therapy, or detrusor underactivity

Consider Other Causes

• New medications (the case report 5 describes venlafaxine causing incontinence in a patient stable on tamsulosin/finasteride)
• Neurological conditions
• Urinary tract infection
• Fecal impaction

The Correct Management Approach

1. Continue both tamsulosin and finasteride - the combination provides superior symptom control and reduces progression risk by 67% compared to placebo 1

2. Measure post-void residual to distinguish between:

   • Low PVR (<100 mL): Suggests OAB → add antimuscarinic (solifenacin, tolterodine) or mirabegron to existing regimen 4
   • High PVR (>200 mL): Suggests inadequate emptying → consider urodynamics, possible surgical intervention

3. Review medication list for new drugs that could cause incontinence (antidepressants, diuretics, sedatives)

4. If finasteride has been used <6-12 months, continue it as the full therapeutic effect takes time to develop 2

Critical Pitfall to Avoid

Stopping finasteride prematurely would be a mistake because:

• It takes 6-12 months to achieve maximal prostate volume reduction 2
• Combination therapy (alpha-blocker + 5ARI) reduces the risk of BPH progression by 67%, acute urinary retention by 81%, and need for surgery by 64% compared to placebo 1
• The patient has "no issues with urination" (presumably good voiding symptoms), suggesting the medications are working for their intended purpose

The incontinence represents a new problem requiring additional evaluation and treatment, not discontinuation of effective BPH therapy.