Is oxybutynin (antimuscarinic) used to treat Benign Prostatic Hyperplasia (BPH)?

Oxybutynin Is Not Recommended for BPH Treatment

Oxybutynin is not indicated for the treatment of benign prostatic hyperplasia (BPH) alone, but may be used as combination therapy with alpha-blockers in men who have both BPH and overactive bladder symptoms.

Primary Treatment Options for BPH

• Alpha-blockers (alfuzosin, doxazosin, terazosin, tamsulosin) are first-line medical therapy for BPH, working by inhibiting alpha1-adrenergic-mediated contraction of prostatic smooth muscle to relieve bladder outlet obstruction 1
• 5-alpha-reductase inhibitors (finasteride, dutasteride) are appropriate for patients with LUTS associated with demonstrable prostatic enlargement 2
• 5-alpha-reductase inhibitors are NOT appropriate treatments for men with LUTS who do not have evidence of prostatic enlargement 2
• Surgical intervention remains appropriate for patients with moderate-to-severe LUTS who have failed medical therapy or developed complications of BPH 2

Role of Antimuscarinics (Including Oxybutynin) in BPH Management

• Antimuscarinics like oxybutynin are primarily indicated for overactive bladder symptoms, not for BPH itself 2
• Oxybutynin and other antimuscarinics may be used as add-on therapy to alpha-blockers in men with residual storage symptoms (urgency, frequency) despite alpha-blocker treatment 2
• MacDiarmid et al. demonstrated that extended-release oxybutynin in combination with tamsulosin was effective for treatment of lower urinary tract symptoms in men with BPH and overactive bladder 2
• Antimuscarinics should be used cautiously in men with BPH due to theoretical risk of urinary retention, though studies show this risk is relatively low when used appropriately 3

Combination Therapy Approach

• When men with BPH have both storage and voiding symptoms, combination therapy with an alpha-blocker plus an antimuscarinic may be more effective than monotherapy 2
• Only 14.8% of men with both storage and voiding symptoms receive concomitant alpha-blocker and antimuscarinic therapy, suggesting potential undertreatment 4
• The combination of alpha-blocker plus muscarinic receptor antagonist is more efficacious in reducing LUTS than either drug alone 5

Practical Considerations

• When considering antimuscarinic therapy in men with BPH:
  • Assess post-void residual volume before initiating therapy 2
  • Monitor for symptoms of urinary retention 3
  • Consider using in combination with an alpha-blocker rather than as monotherapy 2, 4
• Among antimuscarinics used in men with BPH and storage symptoms, solifenacin had the lowest discontinuation rate (43%) compared to other options 4

Cautions and Monitoring

• Theoretical risk of urinary retention exists when using antimuscarinics in men with BPH, though clinical studies show this risk is low 3
• In one study of oxybutynin transdermal system in men with OAB (including those with prostate conditions), only 0.5% experienced mild urinary retention symptoms, and none required catheterization 3
• Regular monitoring of post-void residual volume is recommended when using antimuscarinics in men with BPH 2

Remember that BPH treatment should focus on improving quality of life and reducing the risk of BPH-related complications 6. Oxybutynin alone is not a treatment for BPH but may have a role in managing concomitant storage symptoms in men with BPH who are already on alpha-blocker therapy.