BTX relieves endometriosis-associated chronic pelvic pain

The administration of onabotulinumtoxinA (BTX) led to relief of pain and spasm in premenopausal women with persistent pelvic pain due to endometriosis, a study presented at ESHRE 2022 has shown.

“[As BTX] is commonly used for conditions with muscle overactivity and pain … we evaluated its potential to decrease pelvic floor spasm and ameliorate chronic pelvic pain in women with endometriosis [experiencing these symptoms],” said the researchers. “[Our findings showed that BTX provided relief for] pelvic floor muscle spasm as part of endometriosis-associated pelvic pain … that persisted over time. [BTX] was also well tolerated.”

This National Institutes of Health study comprised 29 premenopausal women with endometriosis who had pain that had persisted for more than 10 years on average despite receiving optimized standard treatment (eg, surgery, hormones). They were randomized to receive an injection comprising 100 U of BTX or placebo into the pelvic floor muscles with palpable spasms. A second injection (BTX) may be administered at least a month after the first injection or any time over the next year should any participant in either arm request for another one. [ESHRE 2022, abstract O-156]

All participants pointed to the pelvic floor as a major focus of pain, and all noted widespread myofascial dysfunction with trigger points in more than 2/3 of the evaluated regions. Nineteen women characterized their pelvic tenderness as focal and non-diffuse. Of the 23 women who were on hormone therapy, 22 had suppression of their menses. Sixteen women reported widespread sensitization.

A majority (n=27) of the participants requested for a second injection; those who did not initially received BTX and reported persistent benefit from it.

At end of study, 16 women reported continued benefit with BTX, while four reported no durable benefit even after the second injection.

Despite the local pain and discomfort reported with the intravaginal injections, no serious side effects were attributed to BTX.

About 30 percent of women with a history of endometriosis may have persistent pelvic pain despite standard care, with accompanying pelvic floor muscle spasms and sensitization within and beyond the pelvis, the researchers noted. The chronicity of the condition not only affects women’s physical wellbeing; it does take a toll on their emotional, mental, and sexual health as well.

Overall, with a majority of the participants reporting benefit and pain relief from BTX, the findings imply that it is more likely to provide benefit than placebo. “Baseline and current disability predicted improvement in pain, sexual intercourse, functioning, fatigue and mental health scores,” the researchers added.

“The findings illustrate a viscerosomatic reflex relationship between endometriosis lesions and muscle spasm, [suggesting] that pelvic floor spasm may initiate or maintain sensitization,” they continued.

“[T]his study supports that [BTX] can safely and effectively treat chronic pelvic pain in women with a history of endometriosis and ongoing spasm in the pelvic floor muscles,” they concluded, calling for further investigation to validate the benefits of BTX in this setting.