Review finds CBD pain trials inconclusive, with liver safety concerns

Cannabidiol (CBD), the principal non-intoxicating phytocannabinoid of Cannabis sativa, is widely marketed and self-administered for pain relief, yet its regulatory status as an analgesic remains unapproved. This review synthesizes preclinical mechanistic data, human pharmacokinetic data, and clinical trial evidence across major pain conditions in order to summarize the current evidence for, or against, efficacy and safety for pain. A synthesis of published information was conducted using PubMed/MEDLINE, PubMed Central, Cochrane Library, ScienceDirect, and other databases, integrating findings from systematic reviews, meta-analyses, randomized controlled trials (RCTs), and pharmacology reviews on CBD (independent of combination products where possible) and pain of any etiology. Preclinical and mechanistic data support plausible physical analgesic pathways for CBD, including receptor modulation, indirect enhancement of endocannabinoid tone via fatty-acid-binding-protein (FABP) inhibition, and anti-inflammatory effects. However, translation to clinical benefit has been inconsistent. In the largest meta-analysis of cannabinoids for pain, cannabinoids reduced chronic pain and improved sleep quality, but effect sizes fell below predefined minimally important clinical differences, and cannabinoids showed no benefit for acute or cancer pain, while increasing non-serious adverse events. CBD randomized trials in knee osteoarthritis, fibromyalgia, and acute low back pain have consistently failed to separate from placebo, whereas smaller/lower-quality trials and observational surveys report subjective benefit. Safety data increasingly point to dose-dependent hepatotoxicity risk. Despite strong biological plausibility and considerable consumer use, current high-quality evidence does not support CBD monotherapy as an effective analgesic across most pain conditions studied to date. Safety monitoring, particularly of liver enzymes at higher doses, is warranted.