Abstract
Introduction: Chronic pain is a prevalent condition that significantly affects individuals' quality of life and functionality. Pharmacological treatments often have limited efficacy or intolerable adverse effects, which encourages the search for complementary therapies. Medical cannabis has emerged as a relevant therapeutic option, especially in cases of neuropathic pain, fibromyalgia, and cancerrelated pain. Its main active constituents, tetrahydrocannabinol (THC) and cannabidiol (CBD), act on the endocannabinoid system, which modulates physiological processes such as pain perception, inflammation, and mood. Objective: To analyze the current scientific evidence on the therapeutic use of medical cannabis in the treatment of chronic pain, focusing on its efficacy, safety, mechanisms of action, and clinical applicability. Methods: This is a narrative literature review conducted through searches in the PubMed, Scopus, and SciELO databases, using the terms ‘medical cannabis’, ‘chronic pain’, ‘cannabinoids’, ‘THC’, and ‘CBD’. Articles published between 2016 and 2024 were included, with priority given to systematic reviews, randomized clinical trials, and clinical guidelines. After analysis of the titles, abstracts, and full texts, 23 studies that met the relevance criteria for the topic were selected. Results: The analysis of the studies revealed that the use of medical cannabis is associated with a significant reduction in chronic pain intensity, particularly in cases of neuropathic pain and pain associated with multiple sclerosis, cancer, and fibromyalgia. The combination of THC and CBD was found to be more effective than the isolated use of either cannabinoid. In a clinical trial conducted by Häuser et al. (2018), patients with chronic noncancer pain who used cannabis preparations reported improvements of up to 30% in pain perception. In the metaanalysis by Whiting et al. (2015), moderate efficacy of cannabis compared with placebo was observed, particularly for neuropathic pain. Another study by Portenoy et al. (2012) demonstrated that the use of nabiximols (an oral spray containing THC and CBD) significantly reduced pain in patients with advancedstage cancer. Additional reported benefits included improvements in sleep, appetite, and quality of life. However, adverse effects such as sedation, dizziness, and cognitive changes were common, particularly at higher doses. Häuser et al. (2021) emphasize that, although the effects are modest, they are clinically relevant in populations refractory to other treatments. The study by Russo (2008) reinforces the relevance of the entourage effect—the synergy among various cannabis compounds—as a potential amplifier of the analgesic effect. Conclusion: Medical cannabis represents a viable alternative for the management of chronic pain, especially in patients refractory to conventional therapies. Its analgesic effects result from modulation of the endocannabinoid system and are more evident in balanced THC/CBD preparations. Although promising, cannabinoid therapy requires caution regarding dosage, formulation, clinical indication, and multidisciplinary monitoring. Limitations remain related to the scarcity of clinical trials with greater methodological rigor, dose standardization, and regulation. The training of healthcare professionals and investment in public policies are essential to promote the safe and rational use of medical cannabis.
