A vaginal baclofen suppository eased chronic pelvic pain in a small randomised trial

Women with chronic pelvic pain who used a nightly vaginal baclofen suppository had a larger reduction in pain than women who used a placebo suppository, according to a small randomised, double-blind trial published on 5 November in the American Journal of Obstetrics and Gynecology [s1]. The result is encouraging for a condition with few targeted treatments — but the trial was deliberately modest in size, and its authors frame it as a reason to run a bigger study, not as settled evidence.

Chronic pelvic pain is common and often difficult to treat. One recognised contributor is dysfunction of the pelvic floor muscles themselves, yet the drug options aimed directly at that mechanism are limited [s1]. Baclofen is a muscle relaxant; delivering it as a vaginal suppository is an attempt to act locally on those muscles while keeping the dose low.

What the trial did

The study was a single-centre, randomised, double-blind, placebo-controlled trial [s1]. It compared a 20 mg baclofen vaginal suppository, used nightly, against an identical-looking placebo suppository.

To enter, women had to be older than 18, have no allergy to baclofen or the suppository base, and report at least 40 out of 100 mm of pain on a visual analogue scale when a clinician pressed on the obturator internus or levator ani — the pelvic-floor muscles — during a standardised examination [s1]. That entry criterion matters: it selected for women whose pain was reproducible on muscle palpation, the group the drug was designed to help.

The primary outcome was the change in that examination pain score, measured on the same 100 mm scale, after eight weeks [s1]. Participants also completed validated questionnaires — the PROMIS measures of pain interference, global health and sexual function — at the start, at four weeks and at eight weeks. The trial was powered in advance to detect a 20 mm difference, the margin the researchers treated as the smallest clinically meaningful change, which required 34 participants, 17 per group [s1].

What it found

Thirty-nine women enrolled and 37 were randomised, 19 to baclofen and 18 to placebo [s1]. The groups were similar at baseline, with a mean age of 42.5 years in the baclofen group and 46.3 in the placebo group, and near-identical body mass index [s1].

On the primary outcome, the baclofen group improved substantially more. The median reduction in examination pain at eight weeks was 33.5 mm with baclofen versus 7.2 mm with placebo (p<0.001) [s1]. Patients' own ratings of their overall pain moved the same way: a median improvement of 32.0 mm with baclofen against 0.0 mm with placebo (p=0.001) [s1].

The other measures were less clear-cut. The validated PROMIS questionnaires — covering pain interference, general health and sexual function — showed no significant differences between the two groups [s1]. On safety, there were no adverse events in the baclofen group; in the placebo group, one participant reported intermittent headaches and one reported irritated vaginal skin [s1].

How to read it

This is a positive trial, and the design was sound for its size: randomised, double-blind, placebo-controlled, and powered in advance for a pre-specified clinically meaningful difference. Within those limits, the finding is clean — eight weeks of nightly baclofen suppositories beat placebo on both examiner-measured and patient-reported pain.

The limits are real, though, and the authors do not hide them. This was a single centre with fewer than 40 women, so the estimates are imprecise and may not generalise. Eight weeks says nothing about whether the benefit lasts, and the gap between the clear improvement in pain scores and the flat questionnaire results is a caution: a drop in examination pain did not translate into measured gains in function or quality of life over the study window [s1].

What to watch

The useful reading is that a locally delivered muscle relaxant is a plausible, apparently well-tolerated option for pelvic-floor-related pain that now deserves a larger, multi-centre trial with longer follow-up — the kind of study that could show whether the pain benefit holds up and whether it eventually improves daily function. For context, see our coverage of chronic pelvic pain and pelvic-floor disorders.

This article describes a single small trial. It is not medical advice, and decisions about pain medication belong with a clinician who knows the individual case.