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The Medical Use of Marijuana in Cancer
This syllabus topic contains critical analyses of the medical literature on the clinical use of medical cannabis to treat cancer-related ailments. The use of cannabinoid-based medicines to treat chemotherapy-induced side effects will be discussed in detail, and cancer pain and other cancer-related ailments will be addressed, as well.
Animal models suggest that cannabinoids can treat as well as prevent chemotherapy-induced peripheral neuropathy in rodents.1-3 Inhaled cannabis has been shown to be effective in the treatment of HIV-related peripheral neuropathy.4 To date, the only human study of a cannabis-based medicine in chemotherapy-induced peripheral neuropathy is a crossover placebo-controlled trial of nabiximols (Sativex) (2.7mg THC and 2.5mg CBD/spray) in 16 patients.5 Overall, there was no difference reported in pain scores between nabiximols and placebo, with a mean dose of 8 sprays per day (21.6 mg THC and 20mg CBD) in the active treatment arm. However, five responders reported a greater than 2 point decrease in their neuropathic pain on a zero to ten point scale. This suggests that 5 patients need to be treated with the sublingual preparation for one to have a clinical benefit. This is an acceptable number needed to treat for a neuropathic condition, and the results suggest further investigation of cannabis medicines in chemotherapy-induced peripheral neuropathy is warranted.
In animal models, cannabinoids have been shown to be synergistic with opioids in reducing pain.6 A small pharmacokinetic interaction study of vaporized cannabis (900mg of 3.56% THC herbal cannabis with no CBD), administered once on days 1 and 5, and three times daily on days 2 - 4 in 21 chronic pain patients on sustained release morphine (10) or oxycodone (11) showed no significant effect on opioid plasma concentrations when cannabis was added but did suggest increased analgesia.7 A randomized controlled trial of nabiximols in 359 cancer patients with poorly controlled pain despite a stable opioid regimen found that the sublingual preparation at 4 sprays (10.8 mg THC and 10 mg THC), 10 sprays (27 mg THC and 25 mg CBD) or 16 sprays (43.2 mg THC and 40 mg CBD) daily for 5 weeks decreased pain and sleep disruption.8