Mirabegron by largely lacking the side effects of anticholinergics might be an interesting therapeutic option in Parkinson's disease patients but has never been assessed in this population so far. The aim of the present study was to assess the safety and efficacy of mirabegron for the treatment of storage symptoms in patients with PD.

All PD patients who were treated with mirabegron 50 mg once daily for storage lower urinary tract symptoms (LUTS) between 2010 and 2017 were included in a retrospective study. The primary endpoint was clinical success defined as any subjective improvement in storage LUTS self-assessed by the patients four weeks after mirabegron initiation. Univariate logistic regression and cox proportional hazards models were used to seek for predictive factors of success and persistence with mirabegron respectively.

Out of 50 patients included, 25 reported their storage LUTS had improved (50%), 23 were unchanged (46%) and 2 had worsened (4%) respectively. Five patients had a complete resolution of their urgency incontinence (11.4%). The number of pads per day decreased significantly after four weeks of mirabegron intake from 1.5 to 0.9 on average (p=0.01) and so did the number of nocturia episodes (from 3 to 2.6/night; p=0.02). Only two adverse events were observed during mirabegron treatment (4%), both of them grade 1 according to the FDA classification: one dizziness and one diaphoresis. After a median follow-up of 19 months, 27 patients had discontinued mirabegron (54%). The median time to discontinuation was 17 months with estimated persistence rate of 51.5%, 44.6% and 36.4% at 1, 2 and 3 years respectively. No predictive factor of success was found in univariate analysis. The only statistically significant predictive factor of longer persistence with mirabegron was male gender (HR=4.94; p=0.002).

Mirabegron may be at least as effective as anticholinergics in PD patients but might be more appropriate carrying a lower risk of adverse events.

In the present series, mirabegron intake resulted in improved storage LUTS in 50% of PD patients and complete urgency incontinence resolution in 11.4% of them, with significant decrease in nocturia and urgency incontinence severity at four weeks. Mirabegron was well tolerated with only two mild adverse events (4%) and no unexpected safety issues. With a median time to discontinuation of 17 months, our data suggested that persistence with mirabegron might be longer in PD than in OAB populations. Further prospective randomized trials are needed to properly assess mirabegron in PD patients.