The most important endpoint in assessing treatments for overactive bladder (OAB) is treatment efficacy. However, OAB is a chronic disease, which makes it important to ensure long-term treatment safety. This is particularly important for older adult patients who often have decreased physiological functions because OAB drugs induce or worsen constipation. However, few existing studies have compared OAB drugs in terms of their effects on elimination in clinical practice. Thus, this study aimed to investigate the elimination changes that OAB patients experience after being administered β3 agonists and anticholinergics, which are the main drugs for OAB.

This was a retrospective study of patients who were newly diagnosed with OAB who were either prescribed a β3 agonist (mirabegron) or anticholinergics (fesoterodine or solifenacin). Changes in OAB symptoms from baseline to 12 weeks of treatment were assessed using the overactive bladder symptom score (OABSS) questionnaire. Elimination at baseline was assessed with the Bristol scale (BS) and constipation scoring system (CSS), and their scores were compared within and between groups. OAB was defined as a score of ≥2 points for Q3 (urgency) and a total score ≥3 points on the OABSS. P<0.05 was considered statistically significant.

Data of 165 patients (mirabegron=56, fesoterodine=52, solifenacin=57) were available for analysis. Total OABSS scores improved significantly in all three groups after treatment (P<0.001 for all). BS decreased significantly from 3.2 ± 1.0 at baseline to 2.3 ± 1.2 after administration in patients taking solifenacin, showing that stools hardened only in the solifenacin group (P<0.001). No changes were observed in any of the CSS items for the mirabegron group; thus, no changes were observed in elimination in patients administered mirabegron. In the fesoterodine group, questionnaire scores for feeling of incomplete evacuation and type of assistance worsened after administration (P<0.001 and P<0.013, respectively). In the solifenacin group, elimination worsened as assessed by almost all items after 12 weeks of treatment. In particular, total modified CSS scores worsened significantly from 4.8 ± 2.6 points at baseline to 8.0 ± 4.8 points 12 weeks later in the solifenacin group (P<0.001). Inter-group comparisons also revealed that both BS and CSS worsened more in the solifenacin group than the other groups that took other drugs, showing poorer elimination status (P<0.001 and P<0.001, respectively).

All three drugs investigated in this study were effective for treating OAB. While almost no change was observed for constipation after mirabegron administration, constipation worsened significantly after solifenacin administration. Among the anticholinergics, fesoterodine was safe for use with regard to elimination.

The findings of this study suggest that a patient’s elimination status should be taken into account when selecting OAB drugs.