Effect of imipramine on urethral opening pressure: A randomized, double-blind, placebo-controlled crossover study in...

In two open-label trials, imipramine alleviated symptoms in patients with stress urinary incontinence and is therefore used off-label for this indication. However, it has never been confirmed that imipramine increases urethral pressure in a placebo-controlled setting. The purpose of this study was to investigate whether imipramine increases the opening urethral pressure compared to placebo in healthy women using urethral pressure reflectometry.

A randomized, double-blind, placebo-controlled, crossover study in 16 healthy women. Opening urethral pressure was measured predose and 1 hour after a single dose of 50 mg imipramine or placebo. The washout period was minimum of 1 week. The study was approved by the local ethics committee, conducted according to the Good Clinical Practice guidelines, and registered on ClinicalTrials.gov and EudraCT before recruitment of subjects. Funding was provided by the clinical department.

There were no dropouts and no serious adverse events. There were 13 adverse drug reactions related to imipramine in seven subjects, one adverse event related to placebo, and two adverse events related to the measurements with urethral pressure reflectometry. Imipramine compared to placebo increased opening urethral pressure in the resting condition with 6.5 cmH₂ O (95% confidence interval [CI]: -0.5, 13.5), P = 0.07, and in the squeeze condition with 7.9 cmH ₂ O (95% CI: -0.3, 16.1), P = 0.06.

In conclusion, the increase in opening urethral pressure after imipramine treatment compared to placebo was neither statistically significant nor clinically relevant, and we do therefore not recommend the off-label use of imipramine for the treatment of stress urinary incontinence.