Can suddenly stopping finasteride (dutasteride) cause increased urine output or changes in urinary symptoms in patients with Benign Prostatic Hyperplasia (BPH)?

Effects of Suddenly Stopping Finasteride on Urinary Output

Suddenly stopping finasteride can potentially cause increased urine output and worsening of urinary symptoms in patients with BPH due to rebound prostatic growth and subsequent urinary obstruction. 1

Mechanism of Action and Effects of Finasteride

• Finasteride is a 5-alpha-reductase inhibitor (5-ARI) that reduces prostate size by blocking the conversion of testosterone to dihydrotestosterone (DHT), the primary hormone responsible for prostatic growth 1
• When taken regularly, finasteride reduces prostate volume by approximately 15-20%, increases peak urinary flow rate, and improves lower urinary tract symptoms (LUTS) in men with enlarged prostates 1
• The drug demonstrates efficacy in reducing the risk of acute urinary retention and the need for BPH-related surgery, with benefits increasing with rising prostate volume or serum PSA levels 1

What Happens When Finasteride is Discontinued

• Upon discontinuation of finasteride, serum DHT levels increase again, likely resulting in the return of prostatic hyperplasia 2
• This prostatic regrowth can lead to:
  • Decreased urinary flow rates
  • Return of obstructive symptoms
  • Potential for increased urinary frequency and urgency 2
  • Possible increased urine output as the bladder compensates for partial obstruction 1

Time Course of Changes After Discontinuation

• The effects of finasteride persist for as long as the medication is taken, with benefits documented for up to 5 years in long-term studies 2
• After discontinuation, DHT levels begin to rise, though the exact timeline for symptom recurrence varies among individuals 2
• The American Urological Association guidelines note that the benefits of finasteride are lost when therapy is withdrawn, necessitating long-term treatment for sustained symptom control 1

Risk Factors for Significant Urinary Changes After Discontinuation

• Men with larger prostate glands (≥40 mL) are at higher risk for symptom recurrence after stopping finasteride 3
• Patients with higher baseline PSA values may experience more pronounced symptom return 1
• Those who had significant symptom improvement while on finasteride (≥3-point improvement on AUA Symptom Index) may notice more dramatic changes when stopping 1

Clinical Implications and Recommendations

• Patients should be counseled about the potential for worsening urinary symptoms if finasteride is discontinued 1
• Abrupt discontinuation may lead to more pronounced symptoms than gradual tapering, though this is not well-studied 2
• Monitoring for signs of acute urinary retention is important in the weeks following finasteride discontinuation, particularly in men with larger prostates 3
• If a patient needs to stop finasteride, consider transitioning to an alpha-blocker to manage symptoms, as these medications work through a different mechanism 4

Common Pitfalls and Caveats

• Not all men will experience significant symptom changes after stopping finasteride; those with smaller prostates (<25 mL) may have minimal effects 3
• The sexual side effects of finasteride (decreased libido, ejaculatory dysfunction, erectile dysfunction) are typically reversible after discontinuation 1
• Patients may confuse increased urinary frequency due to returning obstruction with increased urine output; proper assessment is needed to distinguish between these phenomena 1
• Finasteride has a relatively long-lasting effect on 5-alpha-reductase, so symptoms may not return immediately after discontinuation 2