Studies Demonstrate Cannabinoids Relieve Intractable Pain

Several recent studies have confirmed the effectiveness of cannabis and its constituent components in treating types of pain that are difficult to treat with conventional therapies.

Clinical trials have shown that a whole-plant extract of marijuana relieves intractable cancer pain. The double blind, randomized, placebo-controlled trial found pain scores improved significantly with a cannabis extract compared to placebo or THC alone. Researchers report that the combination of plant cannabinoids in the dosage-controlled cannabis extract Sativex “is an efficacious adjunctive treatment for cancer-related pain” for patients who do not get relief from opiates. Between 25% and 45% of cancer patients experience neuropathic pain, a chronic condition associated with nerve injury.

The effectiveness of cannabis and cannabinoids in relieving neuropathic pain has been demonstrated in more than three dozen preclinical and clinical trials, a new review by researchers at the University of Georgia has found. They note that “a large number of research articles have demonstrated the efficacy of cannabinoids” and conclude “cannabinoids show promise for treatment of neuropathic pain.” [Neurotherapeutics. 2009 Oct;6(4):713-37.]

Several sets of researchers have recently published findings on the efficacy of cannabinoids in treating pain resulting from spinal cord injuries (SCI). A French team, noting that “very few pharmacological studies have dealt specifically with neuropathic pain related to SCI,” suggests that for “refractory central pain, cannabinoids may be proposed on the basis of positive results in other central pain conditions (e.g. multiple sclerosis).” [Ann Phys Rehabil Med. 2009;52(2):124-41.]

Researchers at the University of Miami have demonstrated in an animal model of SCI pain that cannabinoids yield more consistent positive results than conventional analgesics such as opiates, which “decrease in efficacy with repeated treatment over time.” They conclude that drugs targeting the body’s cannabinoid receptors “hold promise for long-term use in alleviating chronic SCI pain.” [J Rehabil Res Dev. 2009;46(1):135-43.]

Enhancement of the body’s natural cannabinoids also holds promise for treating neuropathic pain, according to researchers at Virginia Common-wealth University. Noting that the ability of cannabinoids to reduce pain after nerve injury is “well known,” but “their psychoactive side effects have damped enthusiasm for their therapeutic development,” researchers studied the effect of reducing two enzymes that degrade the body’s natural cannabinoids. They found that inhibiting the enzymes “reduces neuropathic pain through distinct receptor mechanisms of action” that “present viable targets” for developing new drugs. [J Pharmacol Exp Ther. 2009 Sep;330(3):902-10.]

Cannabinoids have been shown to work in concert with opiod drugs in relieving neuropathic pain. Researchers at Mount Sinai School of Medicine suggest that direct and indirect interactions between opioid and cannabinoid receptors not only enhance analgesia but may reduce the development of tolerance to opiates. They conclude studies of such interactions are “critical for understanding how the receptor systems involved in pain relief are altered during acute or chronic pain” so better therapies can be created. [Curr Opin Pharmacol. 2009 Oct 24.]



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