Botulinum toxin relieves endometriosis pain
Botulinum toxin relieved chronic pelvic pain caused by endometriosis, according to data from a small randomized controlled trial presented at the American Society of Reproductive Medicine Scientific Congress & Expo.
“To date, the standard approach to managing the pain from endometriosis has involved surgery to remove endometriosis lesions and using hormones to suppress lesion regrowth,” Pamela Stratton, MD, a staff clinician in the intramural research program within the National Institute of Neurological Disorders and Stroke, told Healio.
“Very little work has been done that examines the relationship between pelvic muscle spasm and pain in women with chronic pelvic pain, on the peripheral and central nervous system sensitization that accompanies chronic pelvic pain in women with endometriosis, or on treatments specifically targeted to this pain,” she said.
Previous research has shown that botulinum toxin, or BoNT, benefited patients with muscle spasm, and over the last 10 years, it has increasingly been used for pain conditions, Stratton added.
For the new study, the researchers randomly assigned 29 women aged 18 to 55 years who reported pelvic pain from endometriosis for a mean of 11.5 years to receive a masked injection that consisted of either 25U/cc of onbotulinumtoxinA under electromyography guidance (n = 15) or saline-based placebo (n = 14). Most of study participants were white and in their 20s or 30s, and about two-thirds of all the women reported feeling at least moderately disabled by their pain. All the women, regardless of treatment received, had the option of receiving a BoNT injection at any time 1 to 12 months after receiving the masked injection.
Stratton and colleagues reported that 1 month after receiving the masked injection, 73% of the women who received BoNT compared with 29% of those who received placebo reported benefits (P = .027). Five of the BoNT recipients and one of the placebo recipients reduced their pain medications intake within 1 month of their injection (P = .23). Over time, Stratton said that 20 study participants reduced or ceased their pain medication intake, with the BoNT recipients using fewer pain medications compared with the placebo recipients (P = .037). There were no significant differences between groups’ Visual Analog Scale scores and ratings.
Only the women who received BoNT experienced a substantial drop in the number of pelvic floor muscles in spasm (P = .019), according to the researchers. The type of spasm and extent of disability did not change between groups.
Adverse events among study participants — the most common of which was urinary hesitancy — were said to be mild, not serious and not different between groups. No women dropped out of the study during the 1-year follow-up period, according to the researchers. Also, two study participants who never received a second injection had long-lasting relief and one became pregnant. Administration of a second injection at 1-month was linked to no benefit (OR = 7.94; 95% CI, 1.2-52.3) and a higher disability at baseline (OR = 1.11; 95% CI, 1.02-1.22). Seven of the placebo recipients and 10 of the BoNT recipients had continued benefit when the study ended.
Stratton cautioned that more research is needed before a change in clinical practice can occur.
“We hope that the planned analysis and reporting of our additional data will advance the field and encourage others to extend our findings and adapt them to clinical practice,” she said in the interview. “Future clinical trials could help define optimal dosage and other aspects of this approach to treatment. Additional information is also needed on the duration of benefit and on the need, timing and frequency of further injections to maintain benefit.”