A prospective randomized clinical trial comparing two doses of AbobotulinumtoxinA for idiopathic overactive bladder.

Aims: To compare 300 U versus 500 U of abobotulinumtoxinA (ABO) intravesical injections for the treatment of idiopathic overactive bladder (OAB) refractory to first and second-line treatments.

Methods: A prospective, randomized, single blind study was performed in female patients with symptoms of OAB, who had failed conservative treatment. Patients were treated with 300 or 500 U of ABO injected into 30 sites, avoiding the trigone. All treatments were evaluated by voiding diary, ICIQ-OAB questionnaire, urodynamic test, visual analogue scale (VAS) for treatment satisfaction and patient global impression of improvement (PGI-I). The primary outcome was change in maximum cistometric capacity (MCC). Secondary outcome included changes in urgency, complete continence, subjective success (VAS and PGI-I), and adverse events (urinary retention, UTI, and CIC).

Results: Twenty-one patients were included. MCC has increased from 185.0 to 270.9 mL (300 U) and from 240.8 to 311.7 mL (500 U), comparing the baseline with 12 weeks, without statistical difference between the groups (P = 0.270). At 12 weeks, 91% of patients were dry in both groups. At 24 weeks, episodes of incontinence had returned in 50% (300 U) and 0% (500 U) (P = 0.013). Patients were better or much better (PGI-I) in70% (300 U) and 88.9% (500 U) at 12 w; and 50% (300 U) and 100% (500 U), at 24 w (P = 0.027). The peak of PVR was at 4 w, being 71.7 mL (300 U) and 96.5 mL (500 U). General UTI incidence was 35.7%. One patient (500 U) required CIC for 2 weeks.

Conclusions: Intravesical ABO injection at 500 U improves symptoms and quality of life for longer period of time than 300 U for idiopathic OAB.