Are cannabis-based medicines a useful treatment for neuropathic pain? A systematic review

Neuropathic pain is a chronic disorder that arises from damaged or malfunctioning nerves. Hypersensitivity to stimuli, also known as hyperalgesia, can cause a person to experience pain from non-painful stimuli, termed allodynia. Cannabis-based medicines (CBMs) may provide new treatment options to manage neuropathic pain. A review of the relevant studies was conducted to evaluate the effectiveness of CBMs in treating neuropathic pain. Scientific literature was systematically searched from January 2003 to December 2024 using the Web of Science Core Collection, PubMed, and MEDLINE. A total of 22 randomized controlled trials (RCTs) were identified that considered the use of 1′,1′-dimethylheptyl-I”(8)-tetrahydrocannabinol-11-oic acid (CT-3), I”(9)-tetrahydrocannabinol (I”(9)-THC), cannabidiol (CBD), combinations of I”(9)-THC with CBD, and cannabidivarin for treatment of neuropathic pain. Significant reductions in pain were reported in 15 studies focused on the treatment of multiple sclerosis, spinal cord injuries, diabetic neuropathy, postherpetic neuralgia, HIV-associated sensory neuropathy, peripheral neuropathic pain, complex regional pain syndrome, chronic radicular neuropathic pain, and peripheral neuropathy of the lower extremities. These positive outcomes often adopted personalized and adjusted dosing strategies. By contrast, seven RCTs observed no significant pain relief compared to placebo, although some had minor improvements in secondary outcomes, such as mood and sleep. Collectively, CBM treatments may improve pain scores, but study limitations such as small sample sizes and study durations, high placebo response rates, and trial unblinding because of the psychoactive effects of cannabinoids all hinder data interpretation and the extrapolation to chronic pain conditions. Hence, future RCTs will need to have larger numbers and be more extended studies that explore optimal dosing and delivery methods and identify patient subgroups that are most likely to benefit. While CBMs show potential, their current use balances modest benefits against possible adverse effects and variable outcomes.

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