Botulinum Toxin for Pelvic Pain: What the Dutch Trial Found

When a treatment aims to relax tense pelvic-floor muscles, a muscle measurement can show whether it had that effect. Pain relief still needs its own assessment. The Dutch botulinum toxin research illustrates why both outcomes belong in the discussion.

The randomized comparison included therapy in both groups

The 2025 trial¹ enrolled 94 women with chronic pelvic pain and increased pelvic-floor tone despite previous muscle therapy. They received 100 units of botulinum toxin A or placebo injections, followed by four pelvic-floor muscle therapy sessions.¹

At 26 weeks, a pain reduction of at least one-third was reported by 15 women (33%) after toxin and nine (20%) after placebo. The difference was not statistically significant (P = 0.19). Eight women in each group (17%) felt much or very much improved.¹

Resting muscle activity decreased significantly more with toxin (P = 0.001). The main pain outcomes did not significantly favor toxin. The manufacturer supplied the toxin, and hospital grants also supported the study.¹

These results concern the injection combined with therapy. They do not isolate injection from therapy, or show that every cause of pelvic pain should receive the same treatment.

What the 2026 extension can add

In the July 2026 extension, 27 women who had not responded to placebo received open-label toxin injections plus further therapy. They knew they were receiving active treatment. Average pain fell from 6.5 to 4.9 on a 0-to-10 scale at 26 weeks. There was no concurrent control group.²

Earlier responders remained improved after both toxin and placebo plus therapy, without a significant between-group difference. Only 19 of the 27 extension participants returned the 12-month questionnaire.²

This was follow-up of selected participants from the earlier research. It was not a second randomized trial. Improvement after a known active injection cannot separate the drug’s effect from further therapy, repeat intervention, changing symptoms or expectations.²

The extension reported two cases of new urge urinary leakage, one mild infection and one temporary defecation difficulty. The small sample limits safety conclusions.²

Why an injection may still appear in a treatment discussion

A 2024 consensus algorithm involving 11 experts placed pelvic-floor physical therapy first and onabotulinumtoxinA injections third for high-tone pelvic-floor dysfunction that had responded poorly to earlier treatment. It explicitly described this use as off-label in the United States. It also advised against repeating injections when the first produced no response.³

That paper was expert consensus, with limited evidence for details of later treatments. Its surveys occurred in 2021, before the Dutch trial results were published. A treatment’s place in an expert pathway and evidence that it outperforms placebo are different questions.

If an injection is proposed, ask what finding supports a muscle-related component of your pain, how the clinician interprets the newer trial, and which alternatives remain appropriate. Chronic pelvic pain can have more than one contributor; the trial’s eligibility criteria should not become a diagnosis made from symptoms alone.

Set a pain goal and a safety plan

Discuss a practical outcome before treatment: sitting comfortably for longer, less pain with a specified activity, or fewer pain-related interruptions. Record the starting point and agree on a review date. A change in muscle activity should be considered alongside the outcome you sought.

The U.S. BOTOX information warns that toxin effects can spread beyond the injection area. Seek immediate medical attention for breathing, swallowing or speech difficulties after treatment. Its potency units are specific to the product and cannot be exchanged directly for another botulinum toxin preparation’s units. Ask which product is proposed and whom to contact about complications.⁴

Down There, Decoded, Chapter 8’s “When Sex Hurts,” explains how to describe pain by location, trigger and duration and ask whether pelvic-floor therapy belongs in the plan. Those details can help an assessment without assuming that all pelvic pain comes from tense muscles.