Magnesium-Based Trigger Point Infiltrations Versus Local Anaesthetic Infiltrations in Chronic Pelvic Myofascial Pain: A Randomized, Double-Blind, Controlled Study.

Objective: To determine if a novel, magnesium-based trigger point infiltration formulation is more effective in treating chronic myofascial pelvic pain than lidocaine-only infiltration.

Methods: This was a single-centre, double-blind, randomized controlled trial of women diagnosed with chronic pelvic myofascial pain associated with trigger points. We compared a novel magnesium-based infiltration formulation with lidocaine infiltration of trigger points and with a control group of participants who were waitlisted for a chronic pain clinic. Treatment groups completed a 12-week program that included 8 trigger point injection treatments and 9 visits during which pain scores were recorded and questionnaires administered. The primary outcome measure was change in mean pain score between baseline and the final visit. Secondary outcomes included pain with function scores, scores on the World Health Organization Quality of Life questionnaire, procedural pain, concomitant medication use, and complications.

Results: We assigned 44 women diagnosed with chronic myofascial pelvic pain associated with trigger points to either the magnesium-based infiltrate (n = 15), lidocaine infiltrate (n = 17), or waitlist (n = 12) group. In the intent-to-treat analysis, a clinically relevant decrease in mean pain score out of 10 was observed in the magnesium-based (-2.6 ± 3.2) and lidocaine (-2.9 ± 3.1) infiltration groups, but not in the waitlist group (-0.5 ± 2.3). The per protocol analysis post-hoc tests, adjusted for multiple comparisons, found a significant difference in the average change in pain score between the magnesium-based infiltrate and the waitlist groups (P = 0.045), while differences between the lidocaine infiltrate and waitlist groups approached statistical significance (P = 0.052). Both treatment groups saw improvements in pain with function and quality of life scores.

Conclusion: While this study is underpowered, it does not support the use of a magnesium-based trigger point infiltrate in the treatment of chronic myofascial pelvic pain over lidocaine-only infiltration. Nonetheless, these results are consistent with current management recommendations and suggest improvements in pain, pain with function, and quality of life scores with either magnesium-based or lidocaine-only infiltration. We outline an approach to assessment and treatment that can be adopted by general gynaecologists.