Medical Cannabis for Gynecologic Pain Conditions: A Systematic Review.

Abstract

The endocannabinoid system is involved in pain perception and inflammation. Cannabis contains delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), which are cannabinoids that bind to endocannabinoid system receptors. A fatty acid amide called palmitoylethanolamide (PEA) enhances endogenous cannabinoids. Given that use of medical cannabis is increasing, we sought to characterize patterns of cannabis use for gynecologic pain and its effectiveness as an analgesic. We searched PubMed, EMBASE, Scopus, Cochrane, and ClinicalTrials.gov using terms for "woman," "cannabis," and "pain" or "pelvic pain" or "endometriosis" or "bladder pain" or "cancer." The search was restricted to English-language articles published between January 1990 and April 2021 and excluded animal studies. The initial search yielded 5,189 articles with 3,822 unique citations. Studies were included if they evaluated nonpregnant adult women who used cannabinoids for gynecologic pain conditions (eg, chronic pelvic pain, vulvodynia, endometriosis, interstitial cystitis, malignancy). Study types included were randomized controlled trials (RCTs), cohort studies, and cross-sectional studies. Covidence systematic review software was used. Fifty-nine studies were considered for full review, and 16 met inclusion criteria. Prevalence of cannabis use ranged from 13% to 27%. Most women ingested or inhaled cannabis and used cannabis multiple times per week, with dosages of THC and CBD up to 70 mg and 2,000 mg, respectively. Sixty-one to 95.5% reported pain relief. All six prospective cohort studies and one RCT of PEA-combination medications reported significant pain relief, and the average decrease in pain after 3 months of treatment was 3.35±1.39 on the 10-point visual analog scale. However, one fatty acid amide enzyme inhibitor RCT did not show pain reduction. Survey data showed that most women reported that cannabis improved pain from numerous gynecologic conditions. Cohort studies and an RCT using PEA-combination medications reported pain reduction. However, interpretation of the studies is limited due to varying cannabis formulations, delivery methods, and dosages that preclude a definitive statement about cannabis for gynecologic pain relief. PROSPERO, CRD42021248057.