Exploratory analysis of the effect of mirabegron on urodynamic sensation parameters and urethral pressure variations

Urethral instability (URI) has in the past been defined by the International Continence Society (ICS), but was excluded from ICS terminology and definitions shortly after because of a lack of consensus about the clinical importance of this phenomenon. Recently, interest in URI and its possible role in overactive bladder (OAB) increased again. In the last decade, a beta 3 adrenoreceptor agonist (mirabegron) was approved for the treatment of OAB. The effect of mirabegron on urethral pressure during filling cystometry is unknown. The aim of this study was to assess the influence of mirabegron on urethral pressure variations during urodynamic investigation and the association of symptoms and voiding diary data before and during treatment.

This prospective study included 51 consecutive adult female patients, referred with OAB. Patients were evaluated using a voiding diary, two validated questionnaires and two urodynamic investigations, one before and one after 6 weeks of treatment with mirabegron. URI was defined as an urethral pressure drop exceeding 30 cmH₂O during filling cystometry.

The prevalence of URI was 31% at initial urodynamic investigation, and 19% at second investigation. URI is more common than DO with 18% prevalence at initial evaluation. Treatment with mirabegron resulted in significant changes in symptoms and urodynamic sensory markers in patients with URI.

Urethral pressure variations are significantly reduced by treatment with mirabegron in patients with URI. URI seems to have a predictive value in treatment choices for OAB. Future research should elucidate this.