Magnesium-Based Trigger Point Injections for Relief of Chronic Myofascial Pelvic Pain

This study will be a randomized, controlled, double-blinded, single-centre superiority trial with two parallel groups. The primary outcome will be average myofascial pelvic pain in the two weeks following final injection treatment as assessed using the visual analogue scale. Randomization will be performed as block randomization with a 1:1 allocation ratio, stratified based on opioid use at the time of study enrollment. In total, 60 participants will be recruited and randomized, with 30 being assigned to each treatment arm. The study will be restricted such that none of the participants enrolled will be current concomitant opioid users (for any reason) and will not have used opioid drugs within the 3 months preceding enrollment in the study.

A third non-randomized arm of 30 participants who are on the waiting list for the chronic pain clinic will be enrolled and compared to the two randomized arms. Among this patient population and in the setting of the Chronic Pain Clinic it was determined that it would not be acceptable to randomize participants to a no-treatment control group. As such, an active treatment is being used as comparator in the randomized trial. In order to assess participants in the absence of treatment this third non-randomized arm will serve as a no-treatment control group.

Eligibility criteria for this third arm is the same as the main study, except for the restriction by opioid use status. Participation in this third arm will not exclude a participant from randomization into one of the two main arms of the study. Therefore, across the three arms, up to 90 patients will be enrolled in this study.

Study Setting: This study will be conducted at the Chronic Pain Clinic at Hotel Dieu Hospital and the General Gynecology Clinic at Kingston General Hospital in Kingston, Ontario, Canada. All of the physicians who provide trigger point injection treatment for chronic pelvic pain in the Chronic Pain Clinic have agreed to participate as co-investigators in this study (RN, RH, and SC). Women are referred to this clinic for treatment of chronic pelvic pain by both primary care providers and gynecologists in the Kingston and surrounding area. Two of the investigators (RN and SC) see patients in the General Gynecology Clinic for assessment and management of chronic pelvic pain. Both investigators regularly refer patients to the Chronic Pain Clinic for consideration of trigger point injections.

Participant Timeline: Participants in this study will be followed for a total of 8 treatments and 9 study visits over a period of 12 weeks. Participants in the third wait-listed arm of the study will be followed for 3 visits over a period of 12 weeks.

Treatment Arms, Baseline Visit \& Treatment 1: At the baseline study visit a research nurse will administer a questionnaire in order to obtain a thorough medical history and collect information on participant demographics. The research nurse will then administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the baseline visit and the WHOQOL-BREF based on the participant's experiences in the 4 weeks preceding the baseline visit. A study investigator will then mix and administer the trigger point injections. The research nurse will remain present for the treatment to assist with recording and administer the VAS pain scale for procedural discomfort immediately following completion of treatment.

Treatment Arms, Follow Up Visits \& Treatments 2-8: In total, participants will be seen for 7 follow up visits with additional treatment. Visits 2 through 4 will be done on a weekly basis and visits 5 through 8 will be done bi-weekly, for a total time of 11 weeks. At these visits a research nurse will administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the visit. The research nurse will ask further questions about concomitant medication usage and screen participants for any adverse event or injection-associated complications. In addition at visit 5 the research nurse will administer the WHOQOL-BREF. A study investigator will then mix and administer the trigger point injections. The research nurse will remain present for the treatment to assist with recording and administer the VAS pain scale for procedural discomfort immediately following completion of treatment.

Treatment Arms, Final Study Visit 9: For participants who undergo a full course of treatment the final study visit will be visit 9 and will occur 12 weeks after the baseline visit. If a woman chooses to conclude treatment early, for any reason, then the final visit will occur earlier than 12 weeks. However, the final visit must always be done at least 1 week after the final trigger point injection treatment. At the final study visit a research nurse will administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the visit and the WHOQOL-BREF based on the participant's experiences in the 4 weeks preceding the visit. The research nurse will ask further questions about concomitant medication usage and screen participants for any adverse event or injection-associated complications. In order to assess blinding participants will be asked which treatment they believed they received and their reasons for this belief. Participants will also be asked if they would recommend the treatment to others experiencing myofascial pelvic pain. Finally, participants will be offered continuation of treatment under the care of the primary investigator with an injection formulation of their choosing if they are still experiencing myofascial pelvic pain.

Wait-List Arm, Baseline, Follow Up and Final Study Visit: At the baseline study visit a research nurse will administer a questionnaire in order to obtain a thorough medical history and collect information on participant demographics. The research nurse will then administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the baseline visit and the WHOQOL-BREF based on the participant's experiences in the 4 weeks preceding the baseline visit. The research nurse will ask further questions about concomitant medication usage. A follow up visit will be completed 5 weeks after the baseline visit. At this visit a research nurse will administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the visit and the WHOQOL-BREF based on the participant's experiences in the 4 weeks preceding the visit. The research nurse will ask further questions about concomitant medication usage. For participants who are on the wait-list for at least 12 weeks the final study visit will occur 12 weeks after the baseline visit. If a woman is on the wait-list for under 12 weeks then the final study visit will occur at her first visit to the Chronic Pain Clinic. At the final study visit a research nurse will administer the VAS pain scale and pelvic pain specific functional questionnaire based on the participant's experiences in the week preceding the visit and the WHOQOL-BREF based on the participant's experiences in the 4 weeks preceding the visit. The research nurse will ask further questions about concomitant medication usage.

Eligibility Criteria:
Potential participants will be screened for eligibility based on the following inclusion and exclusion criteria. All of the following criteria will be used to screen participants for enrollment and randomization into one of the two treatment arms. All of the following criteria except for inclusion criteria number 2 and exclusion criteria number 10 will be used to screen participants for enrollment into the third wait-listed patient arm. These eligibility exceptions are necessary for the third arm as opioid medication may be introduced as temporary medical management for the condition while patients wait for acceptance into the Chronic Pain Clinic.

Inclusion Criteria:

1. Patients with a clinical diagnosis of chronic pelvic pain lasting 6 months or greater
2. Not an opioid user: no opioid analgesic use for relief of chronic pelvic pain within the last 3 months

Exclusion Criteria:

1. Age \<18 years or age \>65 years at the time of study enrollment
2. Pregnancy (currently pregnant or planning to become pregnant during the study period)
3. Known allergy or sensitivity to local anesthetics, dextrose, sodium bicarbonate or magnesium-sulfate
4. A clinical diagnosis of fibromyalgia
5. Having received previous trigger point injections of any formulation for pelvic pain
6. Bleeding disorders (including, but not limited to, hemophilia and von Willebrand disease)
7. Currently receiving anticoagulation therapy (including, but not limited to, coumadins, heparin and its derivatives, direct thrombin inhibitors, and anti-thrombin protein therapeutics; use of low dose aspirin is permitted)
8. Living greater than 50 km to the pain clinic at Hotel Dieu Hospital in Kingston, Ontario, Canada
9. Current opioid analgesic use for a reason other than chronic pelvic pain (including, but not limited to, ongoing opioid dependency or relief of other pain symptoms)
10. Recent opioid analgesic use for relief of chronic pelvic pain; defined as use within the last 3 months but not within the last 2 weeks prior to enrollment