Alpha-Blocker and Antimuscarinic Side Effect Profiles

Introduction to Side Effects

The American Urological Association notes that tamsulosin causes ejaculatory dysfunction, occurring more frequently than with other alpha-blockers 1
The European Urology association reports that tamsulosin use during cataract surgery is associated with intraoperative floppy iris syndrome, requiring ophthalmologist notification before any eye procedures 1, 2

The American College of Physicians found that oxybutynin causes antimuscarinic effects, including dry mouth, constipation, and dyspepsia 3, 4, 5
Oxybutynin has a relative risk of 1.7 (95% CI 1.1-2.5) for discontinuation due to adverse effects, requiring treatment of 16 patients to cause one discontinuation 3
The Annals of Internal Medicine reports that oxybutynin versus tolterodine shows significantly higher discontinuation rates (RR 1.9, 95% CI 1.1-3.3), with 14 patients needed to treat to cause one additional discontinuation 4, 5

Oxybutynin causes multiple anticholinergic symptoms, including dry mouth, asthenia, autonomic nervous system disorders, GI disorders, dyspepsia, nausea, pain, palpitations, rhinitis, and UTI, more commonly than tolterodine 4, 5
The European Urology association notes that if comparing tamsulosin to oxybutynin for combination therapy in men with BPH and overactive bladder, the side effects are additive from different mechanisms 2