Mirabegron versus solifenacin in multiple sclerosis patients with overactive bladder symptoms: a prospective comparative non-randomized study

Abstract Objective To determine the patient-perceived effectiveness and tolerability of mirabegron compared to solifenacin in a multiple sclerosis (MS) population with overactive bladder (OAB) symptoms. Materials and Methods MS patients with OAB symptoms who were not on medication for their urinary symptoms at enrollment were prospectively recruited. Patients enrolled in years 1-2 were prescribed mirabegron, whereas patients enrolled in years 3-4 were prescribed solifenacin. At enrollment and 6-week followup, patients completed several patient reported outcome measures (PROMs). The primary outcome was change in Overactive Bladder Questionnaire Short Form (OAB-q SF) symptom severity and minimal clinically important difference (MCID) achievement. The Patient Assessment of Constipation Symptoms (PAC-SYM) was used to assess bowel function over the treatment period. Results 61 patients were enrolled. The majority of the mirabegron (70%) and the solifenacin (69%) group achieved the OAB-q SF symptom severity MCID. The solifenacin group had a statistically significant greater decrease in its end of study OAB-q SF score (Δ = -37.87 versus -20.43, p=0.02). Constipation improved in the mirabegron group and worsened in the solifenacin group (ΔPAC-SYM =-0.38 versus +0.22; p=0.02), with 30% of patients prescribed solifenacin experiencing worsening above the MCID threshold. Conclusion Among MS patients, we demonstrated similar response rates to mirabegron and solifenacin, with approximately 50-70% achieving each PROM's MCID. Though this small study showed some short-term evidence that improvement in urinary symptom severity was greater with solifenacin, this potential benefit must be weighed against the observed risk of worsening constipation. Further studies are needed to confirm these findings.