Cannabinoids and Pain

There are currently 2 cannabinoids available by prescription in the United States: dronabinol (Marinol) and nabilone (Cesamet). Both are FDA-approved for the management of nausea and vomiting associated with cancer chemotherapy in patients who have not responded to conventional antiemetic treatments.1 Dronabinol is also approved for the treatment of anorexia associated with AIDS. Both dronabinol and nabilone are administered orally. Dronabinol is a synthetic form of delta-9-tetrahydrocannabinol (THC)—the psychoactive ingredient of cannabis. Nabilone is also a synthetic cannabinoid that is similar to THC but appears to be more potent.

Although no cannabinoids are currently FDA-approved as analgesics, there is ongoing research on their efficacy. A recent study on use of nabilone in patients with fibromyalgia found a significant reduction in pain compared with placebo.2 Patients receiving nabilone reported significantly more adverse effects, including drowsiness, but none of these were considered serious. Nabilone is also being studied in the United States for its efficacy in neuropathic pain associated with cancer chemotherapy.

Sativex, a combination of THC and cannabidol (the latter agent is not psychoactive), is in phase 3 trials in the United States for relief of cancer-related pain. Sativex is approved in Canada for the treatment of neuropathic pain associated with multiple sclerosis and as an adjunctive analgesic for moderate to severe pain in patients with cancer who have pain despite strong opioid therapy. Unlike dronabinol and nabilone, Sativex is administered in an oral spray.

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