RESUMEN
OBJECTIVES: As a proof-of-mechanism (POM) study of drugs developed to treat stress urinary incontinence (SUI) has not been conducted, this urodynamic study in healthy women was performed to determine an appropriate method to confirm POM, and to evaluate the effect of duloxetine, a serotonin and noradrenaline reuptake inhibitor, on urethral resting pressure and on sphincter contractility in response to coughing and magnetic stimulation. METHODS: The urethral pressure profiles at rest, during coughing and during sacral root magnetic stimulation (SMS), and the motor threshold (MT) for urethral sphincter contraction in response to transcranial magnetic stimulation (TMS) were measured before and 6 h after the administration of 40 mg duloxetine in 10 healthy female subjects. RESULTS: Oral administration of duloxetine significantly increased the mean and maximal urethral closure pressures at rest over the proximal and middle third of the urethra. During coughing, duloxetine marginally significantly increased the mean distal urethral pressure and significantly reduced the mean delay in the distal urethral pressure peak relative to the vesical peak. Although duloxetine did not change amplitudes of pressure spikes in response to SMS, this drug significantly lowered the MT in response to TMS. CONCLUSION: The proposed method for measuring the urethral resistance in healthy women can be used in POM studies of new drugs developed to treat SUI. CLINICAL TRIAL REGISTRATION NUMBER: UMIN000009096.