To assess whether intraurethral anesthesia decreased voiding efficiency (VE), reduced catheterization pain, and impacted urodynamic parameters in healthy adult females.

In a randomized, double-blind, placebo-controlled trial, participants received two 5 mL doses of either intraurethral aqueous gel or 4% lidocaine gel. The primary outcome was VE during randomized condition uroflow, defined as voided volume/(voided volume + residual volume). The secondary outcomes were pain during catheterization and to confirm previously reported pressure-flow changes. A sample size of 10 per group was planned to detect a clinically significant decrease in VE with a power (1-β) of 0.99.

From October to December 2018, 23 women were screened and 18 were randomized to receive placebo (n = 10) or lidocaine (n = 8). Baseline uroflow VE was similar between the placebo and lidocaine groups (88 ± 6.6% vs 91 ± 5.8%, P = .33). After study drug administration, the changes in VE (post-pre) were similar between placebo and lidocaine groups (−5.4 ± 14% vs 1.7 ± 6.4%, P = .21). Visual analog scores were similar following catheterizations (26.7 ± 12.8 mm vs 36.9 ± 26.8 mm, P = .34). The lidocaine group exhibited lower average flow rates per voided volume (0.04 ± 0.02 s⁻¹ vs 0.02 ± 0.01 s⁻¹, P = .04).

Intraurethral administration of 4% lidocaine did not decrease VE compared to placebo and did not change pain scores following catheterization. In the lidocaine group, the average flow rate per voided volume was lower. The decrease in flow rate after local anesthesia to the urethra may indicate that urethral sensory feedback contributes to voiding in human micturition.