Mirabegron is an established treatment alternative to antimuscarinic therapy for patients with overactive bladder (OAB), as shown by efficacy and tolerability data from phase III trials. In our study we aimed to assess efficacy and tolerability of mirabegron versus  botulinum neurotoxin type A (BoNT/A) injection for the treatment of overactive bladder in patients older than ≥65 years-old who were not satisfied with anticholinergic monotherapy for 8 weeks or longer.

This is a retrospective, multi-centre study. We evaluated all patients who have been treated with intradetrusor injection of 100 U of BoNT/A and mirabegron 50mg/day between March 2017 and  February 2019. Patients with urgency and/or urge incontinence due to neurological disorders, history of prior urinary BoNTA injection, previous pelvic surgery, stress-dominant urinary incontinence, were excluded from the study.
Efficacy assessments included micturition frequency, urgency urinary incontinence, pad usage, and nocturia. Health related quality of life and subjective satisfaction rate of the patients were evaluated with Incontinence-QoL (I-QoL) questionnaire at pre-treatment and at 6 months post-treatment. All adverse events were recorded in subjects

Overall, 60 patients included into the study and they received  either mirabegron (n=30) or  BoNT/A (n=30). Table 1 shows description of cohorts of patients. On comparing the pre-treatment data with the 6 month post-treatment duration, a statistically significant decrease was recorded in the frequency, nocturia, daily pad usage and incontinence episodes  in both groups. Median (interquartile range) voiding frequency was lower after BoNT/A compared with mirabegron (9.4 [6.83–10.0] vs 10.5 [8.37–11.67]; p <0.01) at 6 month post-treatment. Similar differences were seen in incontinence episodes (1.3 [1.17–3.67] vs 2.53 [2.0–5.67]; p < 0.05) and nocturia (1.26 [0–4.33] vs 1.7 [1.33–3.33]; p < 0.0001).Urinary tract infection (31% vs 11%; p=0.0003) and voiding difficulty requiring self-catheterisation (16% vs 4%; p=0.003) were more common after BoNT/A.The findings of the I-QoL scores analysis revealed that using mirabegron was preferable compared with BoNT/A as the second-line treatment. (Table 2).

However, in our study, we determined that mirabegron led to less urinary retention, hematuria, infection and PVR rates when compared to BoNT/A in older patient population. In addition, mirabegron treatment had comparable I-QoL scores at post-treatment 6 month. Our results showed mirabegron as an beta 3 agonist  provided similar benefit-to-risk ratio as obtained by BoNT/A and therefore can be considered in treatment of OAB patients who failed to respond to anticholinergic treatment.

Mirabegron as an beta 3 agonist can be considered in treatment of OAB patients who failed to respond to anticholinergic treatment.