OnabotulinumtoxinA is a well-tolerated and effective treatment for overactive bladder (OAB). Transient increases in post void residual volume (PVR) have been reported following onabotulinumtoxinA treatment with some cases requiring clean intermittent catheterization (CIC). Increases in PVR after onabotulinumtoxinA treatment may be a driver for follow-up and initiation of CIC in real-world practice. The rate of the complete inability to void has not previously been reported. This pooled analysis in patients with OAB sought to evaluate the maximum PVR (maxPVR) after onabotulinumtoxinA 100U treatment, subsequent CIC use, and the rates of spontaneous versus non-spontaneous voiding.

This was a pooled post hoc analysis of two phase 3 studies (ClinicalTrials.gov: NCT00910845 and NCT00910520). Patients (males and females) were stratified based on maxPVR measured within 12 weeks after initial onabotulinumtoxinA 100U treatment into groups of 100 mL increments (0-100 mL, 101-200 mL, 201-300 mL, 301-400 mL, 401-500 mL, 501-600 mL, and ≥601 mL). Rates of clean intermittent catheterization (CIC) were assessed at each maxPVR category and rates of spontaneous and non-spontaneous voiding were calculated. Per phase 3 protocols, CIC was initiated if PVR was ≥200 to <350 mL with relevant associated symptoms assessed by the investigator, or if PVR was ≥350 mL regardless of symptoms. Both studies were performed in compliance with Good Clinical Practice regulations and were approved by the institutional review board or Independent Ethics Committee at each site prior to study initiation. All patients provided written informed consent prior to initiation of any study treatment.

This analysis included 551 patients treated with onabotulinumtoxinA. Most patients had a maxPVR ≤200 mL (494/551, 89.7%) and few patients had a maxPVR ≥201 mL (57/551, 10.3%). Most episodes of significantly raised PVR occurred within the first 2 weeks. Those patients in the highest maxPVR category (≥601 mL, n=5) appeared to be older. In total, 36/551(6.5%) patients receiving onabotulinumtoxinA required CIC throughout the study and was highest in patients with maxPVR >300 mL (25/30, 83.3%) versus ≤300 mL (11/521, 2.1%). No consistent trend in mean CIC duration was observed across the PVR subgroups (39-106 days). Of the 551 patients treated with onabotulinumtoxinA, one patient (0.2%) was unable to spontaneously void, this patient had a PVR ≥601 mL (Figure).

In this pooled analysis few patients had a maxPVR ≥200 mL after treatment with onabotulinumtoxinA for OAB. Overall, the rates of CIC were low, and CIC was used primarily in patients in the higher maxPVR categories, as required based on the study protocols. The duration of CIC did not appear to correlate with maxPVR.

This analysis suggests that the vast majority of patients (99.8%) receiving onabotulinumtoxinA do not develop a complete inability to void; seen here in only one patient. All other patients that initiated CIC were still able to spontaneously void and so did not meet the International Continence Society’s definition of urinary retention (inability to pass urine despite persistent effort).