Can prazosin cause urinary problems?

Prazosin and Urinary Problems

Yes, prazosin can cause urinary problems, most notably urinary incontinence (particularly stress incontinence in women) and worsening of lower urinary tract symptoms, despite being an alpha-blocker theoretically used to treat such symptoms.

Mechanism of Urinary Side Effects

• Prazosin works by blocking alpha-1 adrenergic receptors, which relaxes smooth muscle in both blood vessels and the urinary tract 1
• This alpha-1 receptor blockade causes relaxation of urethral smooth muscle, which can significantly impair urethral closure mechanisms 1
• The resulting decrease in urethral tone leads to reduced urethral closure pressure and functional urethral length 1

Specific Urinary Problems Caused by Prazosin

Stress Incontinence (Particularly in Women)

• In women taking prazosin, the incidence of genuine stress incontinence is significantly higher (86.2%) compared to women not taking prazosin (65.7%) 1
• Among women with prazosin-related urinary incontinence, all cases involved stress incontinence 1
• Urodynamic studies demonstrate that prazosin causes significant decreases in functional urethral length, maximum urethral closure pressure, and abdominal pressure transmission to the urethra 1
• When prazosin is discontinued, 25 out of 45 women (56%) had their urinary incontinence improved or cured 1

Limited Efficacy for BPH Treatment

• The American Urological Association does not recommend prazosin for treating BPH symptoms due to insufficient data supporting its effectiveness 2
• Other alpha blockers (alfuzosin, doxazosin, tamsulosin, terazosin) have more robust clinical evidence and are preferred for BPH treatment 2, 3
• While some older studies showed prazosin could improve urinary flow rates in men with BPH 4, 5, the evidence is limited compared to other alpha-blockers 6

Clinical Implications and Management

When Prazosin-Related Incontinence is Suspected

• Consider prazosin withdrawal as a first-line intervention for women presenting with new-onset or worsening stress incontinence while on this medication 1
• This is particularly important in women who have had previous bladder neck surgery, as over 50% of women with prazosin-related incontinence had prior surgical procedures 1
• Avoid unnecessary surgical interventions for incontinence without first attempting prazosin discontinuation 1

Alternative Antihypertensive Options

• If prazosin is being used for hypertension and urinary problems develop, switch to alternative antihypertensive agents that do not affect urethral function 1
• In men with both hypertension and BPH, alpha blockers like terazosin should not be assumed to constitute optimal management of concomitant hypertension 3

For BPH Management

• If prazosin is being used for BPH, switch to evidence-based alpha blockers: alfuzosin, doxazosin, tamsulosin, or terazosin 2, 3
• Terazosin produces a 4-6 point improvement in AUA Symptom Index and -3.7 points in IPSS compared to placebo 3
• Consider adding a 5-alpha-reductase inhibitor for patients with enlarged prostates (>30-40cc) for disease modification 2

Common Pitfalls to Avoid

• Do not overlook prazosin as a cause of new-onset urinary incontinence, especially in women—it is frequently unrecognized 1
• Do not proceed with surgical interventions for stress incontinence without first attempting medication withdrawal 1
• Do not use prazosin as a first-line agent for BPH when better-studied alternatives exist 2
• Remember that prazosin's effects on urethral function persist throughout treatment and are not limited to initial dosing 1