Application of methylene blue as an improvement of the injection technique of botulinum toxin A in the treatment of refractory idiopathic overactive bladder: prospective, single-blind (patient-blind), randomized trial

Introduction
Refractory idiopathic overactive bladder (RIOAB) is a common condition with a significant negative impact on quality of life. Intravesical injection of botulinum toxin A (BTX-A) is widely used as an intervention for these cases. In the standard method the drug solution is colorless. The addition of dye such as methylene blue (MB) facilitates visualization during the procedure and may have a beneficial effect.

Aim
To evaluate the injection of BTX-A with the addition of methylene blue (MB) against a standard method in the treatment of RIOAB.

Material and methods
In this 1-center, single-blinded, randomized controlled trial, we recruited 80 patients with RIOAB. A total of 39 were assigned to injection into the bladder wall of 100 U BTX-A with MB (in 9.5 ml normal saline + 0.5 ml MB), and 41 were assigned to BTX-A 100 U alone (in 10 ml normal saline). Cystoscopy with a submucosal injection of the solution was performed systematically, including the bladder triangle. Participants were assessed 6 and 12 weeks after the treatment using a Likert scale and OABSS questionnaire.

Results
Significant improvement was similar (result of 1 or 2 on the Likert scale) and was achieved in 66.7% and 69.2% after 6 weeks and in 63.9% and 64.1% after 12 weeks in the BTX-A + MB group and only-BTX-A group, respectively. There was a significant difference between the two groups (p = 0.049) in the total number of patients with complications: 2 (5.6%) vs. 9 (23.1%).

Conclusions
The addition of MB to BTX for treatment of RIOAB patients does not influence treatment efficacy, while it limits the risk of complications.