An injection of botulinum toxin, commonly known as Botox, helped relieve chronic pelvic pain in women with endometriosis for up to 11 months, according to researchers.

The results of their study were recently presented at the 2018 Annual Meeting of the American Academy of Neurology in a presentation titled, “Botulinum Toxin Treatment of Chronic Pelvic Pain in Women with Endometriosis.”

Pelvic pain associated with pelvic floor spasms is a problem that persists in women with endometriois, even after they undergo surgery.

Researchers offered women suffering from endometriosis-associated chronic pelvic pain an open injection of the botulinum toxin, called onabotulinumtoxinA, or onaBoNTA. Patients were participating in an ongoing placebo-controlled trial with the toxin.

Ten out of 13 women participating in the study requested the onaBoNTA injection, which was injected into the pelvic floor muscle in 100-unit doses (25 units/cc).

Patients were followed for at least three months after the injection and researchers assessed the injection effects by measuring the changes in spasm, pain, and disability.

At the beginning of the study (baseline, before their injection), eight of the 10 women who elected to get the injection had spasms in their pelvic muscles, accompanied by intense pain.

One month after the onaBoNTA injection, spasm rates were significantly reduced or completely absent from all patients. Most of the patients (eight out of 10) reported only mild or even an absence of pain. Their median score on a scale for measuring pain intensity, called  the visual analogue scale, or VAS, was 1.5.

The VAS scale goes from “no pain” (score of 0) and “pain as bad as it could be” or “worst imaginable pain” (the scale can be as high as 100). As a result, half of the women reduced their need for pain medication.

The disability was also improved in three of five women who showed a moderate disability prior to injection.

The effects of the onaBoNTA injection faded in three women six to 11 months after the injection. The three requested a new shot of onaBoNTA. Adverse events were mild and transient.

Overall, these findings show that “injection of onaBoNTA reduced pain, spasm, and disability for up to 11 months,” researchers wrote.

“Utility of botulinum toxin for endo-CPP [endometriosis-associated chronic pelvic pain] merits evaluation in controlled clinical trials,” the study concluded.