Long-Term Efficacy of Mirabegron Add-On Therapy to Antimuscarinic Agents in Patients With Spinal Cord Injury

Abstract

Objective: To evaluate the long-term efficacy of mirabegron add-on therapy in patients with spinal cord injury (SCI) based on an urodynamic study.

Methods: This retrospective study involved a chart audit of individuals with SCI who underwent two consecutive urodynamic studies between April 1, 2015 and April 1, 2018. After adding 50 mg of mirabegron once a day to the pre-existing antimuscarinic therapy for a period of, at least 6 months, the following variables were analyzed: change in cystometric capacity, change in bladder compliance, change in maximal detrusor pressure, change in reflex volume, and presence of significant leakage during filling cystometry.

Results: A total of 31 participants with a mean age of 41±15 years were included in the analysis. A significant increase in cystometric capacity (mean, 362 to 424 mL; p=0.03), reflex volume (mean, 251 to 329 mL; p=0.02), and bladder compliance (median, 12 to 18 mL/cmH2O; p=0.04) was observed. The presence of leakage during filling cystometry was significantly reduced (29% to 10%; p=0.03). Likewise, a non-significant decrease in the change in maximal detrusor pressure was observed (mean, 31 to 27 cmH2O; p=0.39).

Conclusion: Adding mirabegron to conventional antimuscarinics further improved urodynamic parameters in patients with chronic SCI, and sustained efficacy was observed in long-term use.

Keywords: Mirabegron; Muscarinic antagonists; Spinal cord injuries; Urodynamics.

Fig. 1.

Changes in cystometric capacity (A), reflex volume (B), maximal detrusor pressure (C), and leakage during filling cystometry (D) in participants before and after adding mirabegron (50 mg a day). *p<0.05.

Fig. 2.

Box plots of compliance (mL/cmH2O) in participants before and after adding mirabegron (50 mg a day). *p<0.05.