As many as one in five Americans lives with chronic pain. Many of these people suffer from neuropathic pain (nerve-related pain) — a condition that is associated with numerous diseases, including diabetes, cancer, multiple sclerosis, and HIV. In most cases, the use of standard analgesic medications such as opiates and NSAIDS (non-steroidal anti-inflammatory drugs) is ineffective at relieving neuropathic pain.
Survey data indicates that the use of cannabis is common in chronic pain populations[2] and several recent FDA-designed clinical trials indicate that inhaled marijuana can significantly alleviate neuropathic pain. These include a pair of randomized, placebo-controlled clinical trials demonstrating that smoking cannabis reduces neuropathy in patients with HIV by more than 30 percent compared to placebo.[3-4](Additional details on these studies appear in the HIV section of this book.) In addition, a 2007 University of California at San Diego double-blind, placebo-controlled trial reported that inhaled cannabis significantly reduced capsaicin-induced pain in healthy volunteers[5] A 2008 University of California at Davis double-blind, randomized clinical trial reported both high and low doses of inhaled cannabis reduced neuropathic pain of diverse causes in subjects unresponsive to standard pain therapies.[6] Finally, a 2010 McGill University study finding that smoked cannabis significantly improved measures of pain, sleep quality and anxiety in participants with refractory pain for which conventional therapies had failed.[7]
Preclinical data indicates that cannabinoids, when administered in concert with one another, are more effective at ameliorating neuropathic pain than the use of a single agent. Investigators at the University of Milan reported in 2008 that the administration of single cannabinoids such as THC or CBD produce limited relief compared to the administration of plant extracts containing multiple cannabinoids, terpenes (oils), and flavonoids (pigments).
Researchers concluded: “[T]he use of a standardized extract of Cannabis sativa … evoked a total relief of thermal hyperalgesia, in an experimental model of neuropathic pain, … ameliorating the effect of single cannabinoids,” investigators concluded. … “Collectively, these findings strongly support the idea that the combination of cannabinoid and non-cannabinoid compounds, as present in [plant-derived] extracts, provide significant advantages in the relief of neuropathic pain compared with pure cannabinoids alone.”[8]
In 2009, an international team of investigators from the United Kingdom, Belgium and Romania affirmed these preclinical findings in a clinical study of intractable cancer pain patients. They concluded: “[I]n this study, the THC/CBD extract showed a more promising efficacy profile than the THC extract alone. This finding is supported by evidence of additional synergy between THC and CBD. CBD may enhance the analgesic potential of THC by means of potent inverse agonism at CB2 receptors, which may produce anti-inflammatory effects, along with its ability to inhibit immune cell migration. … These results are very encouraging and merit further study.”[9]
Additional clinical trials assessing inhaled cannabis and chronic pain remain ongoing.[10]
REFERENCES
[1] New York Times. October 21, 1994. “Study says 1 in 5 Americans suffers from chronic pain.”
[2] Cone et al. 2008. Urine drug testing of chronic pain patients: licit and illicit drug patterns. Journal of Analytical Toxicology 32: 532-543.
[3] Abrams et al. 2007. Cannabis in painful HIV-associated sensory neuropathy: a randomized placebo-controlled trial. Neurology 68: 515-521.
[4] Ellis et al. 2008. Smoked medicinal cannabis for neuropathic pain in HIV: a randomized, crossover clinical trial. Neuropsychopharmacology 34: 672-80.
[5] Wallace et al. 2007. Dose-dependent effects of smoked cannabis on Capsaicin-induced pain and hyperalgesia in healthy volunteers Anesthesiology 107: 785-796.
[6] Wilsey et al. 2008. A randomized, placebo-controlled, crossover trial of cannabis cigarettes in neuropathic pain. Journal of Pain 9: 506-521.
[7] Ware et al. 2010. Smoked cannabis for chronic neuropathic pain: a randomized controlled trial. CMAJ 182: 694-701.
[8] Comelli et al. 2008. Antihyperalgesic effect of a Cannabis sativa extract in a rat model of neuropathic pain. Phytotherapy Research 22: 1017-1024.
[9] Johnson et al. 2009. Multicenter, double-blind, randomized, placebo-controlled, parallel-group study of the efficacy, safety and tolerability of THC: CBD extract in patients with intractable cancer-related pain. Journal of Symptom Management 39: 167-179.
[10] University of San Diego Health Sciences, Center for Medicinal Cannabis Research. February 11, 2010. Report to the Legislature and Governor of the State of California presenting findings pursuant to SB847 which created the CMCR and provided state funding.