Botulinum toxin type A for chronic pain and pelvic floor spasm in women: a randomized controlled trial.

OBJECTIVE: To estimate whether botulinum toxin type A is more effective than placebo at reducing pain and pelvic floor pressure in women with chronic pelvic pain and pelvic floor muscle spasm.

METHODS: This study was a double-blinded, randomized, placebo-controlled trial. All participants presented with chronic pelvic pain of more than 2 years duration and evidence of pelvic floor muscle spasm. Thirty women had 80 units of botulinum toxin type A injected into the pelvic floor muscles, and 30 women received saline. Dysmenorrhea, dyspareunia, dyschezia, and nonmenstrual pelvic pain were assessed by visual analog scale (VAS) at baseline and then monthly for 6 months. Pelvic floor pressures were measured by vaginal manometry.

RESULTS: There was significant change from baseline in the botulinum toxin type A group for dyspareunia (VAS score 66 versus 12; chi2 = 25.78, P < .001) and nonmenstrual pelvic pain (VAS score 51 versus 22; chi2 = 16.98, P = .009). In the placebo group only dyspareunia was significantly reduced from baseline (64 versus 27; chi2 = 2.98, P = .043). There was a significant reduction in pelvic floor pressure (centimeters of H2O) in the botulinum toxin type A group from baseline (49 versus 32; chi2 = 39.53, P < .001), with the placebo group also having lower pelvic floor muscle pressures (44 versus 39; chi2 = 19.85, P = .003).

CONCLUSION: Objective reduction of pelvic floor spasm reduces some types of pelvic pain. Botulinum toxin type A reduces pressure in the pelvic floor muscles more than placebo. Botulinum toxin type A may be a useful agent in women with pelvic floor muscle spasm and chronic pelvic pain who do not respond to conservative physical therapy.

CLINICAL TRIAL REGISTRATION: Australian Clinical Trials Registry, https://www.actr.org.au/, ACTRN012605000515695 LEVEL OF EVIDENCE: I.