Previous clinical observations showed that Botulinum A toxin (BoNT/A) has also an antinociceptive effect and can control the neuropathic pain.

In the urologic field, recent in in vitro and in in vivo studies demonstrated that the neurotoxin is able to inhibit the release of several neurotransmitters from the bladder afferent fibers and urothelium. These neurotrasmitters as SP, CGRP, ATP, NGF and Prostaglandins are involved in neurogenic inflammation. Thus, it is reasonable to hypothesize that patients with affected by painful bladder syndrome (PBS) could benefit from BoNT/A intravesically administered.

The aim of the study is to investigate the clinical and urodynamic effects of an intravesical treatment with BoNT/A in patients affected by PBS associated with increased urinary frequency, who are refractory to conventional treatments. This treatment will be compared to bladder over distention, which is considered a conventional therapy.

Patients with refractory PBS will be prospectively enrolled in the study. Baseline evaluation: Clinical evaluation with visual analog scale (VAS) for pain quantification; QoL assessment with a standardized questionnaire, HAM-A and HAM-D scales for the evaluation of anxiety and depression; voiding diary with the recording of diurnal and nocturnal urinary frequency; urodynamic evaluation, 1 month before commencing the study.

Treatment: According to a computerized randomization, patients will receive: A) one single injection of BoNT/A, 100 U diluted in 10 ml normal saline into the bladder, under cystoscopic guidance, under local anesthesia ; or B) one single bladder overdistension under local anesthesia. C) one single injection of placebo (NACL 0.9 % 10 ml) under local anesthesia.

Follow up: clinical evaluation (VAS, HAM-A and HAM-D, QOL assessment, voiding diary) and urodynamics three months after treatment.

Inclusion Criteria:

• refractory bladder pain, the urgency-frequency syndrome, and sterile urine

Exclusion Criteria:

• neurological diseases
• pregnancy and concomitant use of aminoglycosides and anticoagulants