The anticholingeric effects of triprolidine may worsen symptoms in patients with symptomatic prostatic hypertrophy or bladder obstruction. Antihistamines have the potential to adversely affect urinary function, which was demonstrated in a cross-sectional study that evaluated the relationship between medication use and urinary symptoms as measured by the American Urological Association Symptom Index (AUASI) score. AUASI assesses the severity of urinary symptoms such as urgency, frequency, incomplete emptying, and nocturia with higher scores indicating worsening severity. In a random sample of 2115 males ages 40—79 years, 23 reported regular daily use of antihistamines. The age-adjusted mean AUASI score for those taking antihistamines was 8.4 compared to 6.3 in those with no routine medication use (n = 1087), with the difference being statistically significant (2.3; 95% CI 0.3—4.3; p = 0.03). In the antihistamine group, 14 of 23 men (61%) had moderate or severe symptoms (AUASI >= 8).