Medication effects on periurethral sensation and urethral sphincter activity

The aim of this study was to characterize urethral neuromuscular function before and 2 weeks after medication therapy.

Premenopausal women without lower urinary tract symptoms were randomly allocated to 1 of the 6 medications for 2 weeks (pseudoephedrine ER of 120 mg, imipramine of 25 mg, cyclobenzaprine of 10 mg, tamsulosin of 0.4 mg, solifenacin of 5 mg, or placebo). At baseline and after medication, participants underwent testing: quantitative concentric needle electromyography (CNE) of the urethral sphincter using automated multimotor unit action potential software, current perception threshold (CPT) testing to measure periurethral sensation, and standard urodynamic pressure flow studies (PFS). Nonparametric tests were used to compare pre-post differences.

Fifty-six women had baseline testing, 48 (85.7%) completed follow-up CNE, and 49 (87.5%) completed follow-up CPT and PFS testing. Demographics showed no significant differences among medication groups with respect to age (mean, 34.3; SD, 10.1), body mass index (mean, 31.8; SD, 7.5), parity (median, 1; range, 0-7), or race (14% Caucasian, 80% African American). The PFS parameters were not significantly different within medication groups. No significant pre-post changes in CNE values were noted; however, trends in amplitudes were in a direction consistent with the expected physiologic effect of the medications. With CPT testing, a trend toward increased urethral sensation at the 5-Hz stimulation level was observed after treatment with pseudoephedrine (0.15-0.09 mA at 5 Hz, P = 0.03).

In women without lower urinary tract symptoms, pseudoephedrine improved urethral sensation but not urethral neuromuscular function on CNE or PFS. Imipramine, cyclobenzaprine, tamsulosin, solifenacin, and placebo did not change urethral sensation or neuromuscular function.