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Mind

More on Medical Marijuana

Neuroskeptic iconNeuroskepticBy NeuroskepticNovember 15, 2009 3:07 AM

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Previously I wrote about a small study finding that smoked marijuana helps with HIV-related pain. In the last month, two more clinical trials of medical marijuana - or rather, marijuana-based drugs - for pain have come out.

First, the good news. Johnson et al tested a mouth spray containing the two major psychoactive chemicals in marijuana, THC and CBD. Their patients were all suffering from terminal cancer, which believe it or not, is quite painful. Almost all of the subjects were already taking high doses of strong opiate painkillers: a mean of 270 mg morphine or equivalent each day, which is enough to kill someone without a tolerance. (A couple of them were on an eye-watering 6 grams daily). Yet they were still in pain.

Patients were allowed to use the cannabinoid spray as often as they wanted for 2 weeks. Lo and behold, the THC/CBD spray was more effective than an inactive placebo spray at relieving pain. The effect was modest, but statistically significant, and given what these people were going through I'm sure they were glad of even "modest" effects. A third group got a spray containing only THC, and this was less effective than the combined THC/CBD - on most measures, it was no better than placebo. THC is often thought of as the single "active ingredient" in marijuana, but this suggests that there's more to it than that. This was a relatively large study - 177 patients in total - so the results are pretty convincing, although you should know that it was funded and sponsored by GW Pharma, whose "vision is to the global leader in prescription cannabinoid medicines". Hmm.

The other trial was less promising, although it was in a completely different group - patients with painful diabetic neuropathy. The people in this study were in pain despite taking tricyclic antidepressants, which, curiously, are quite good at relieving neuropathic pain. Again, the treatment was a combined CBD/THC spray, and this trial for lasted 12 weeks. The active spray was no more effective than the placebo spray this time around - both groups improved a lot. This was a small trial (just 29 patients), so it might just have not been big enough to detect any effect. Also, this one wasn't funded by a pharmaceutical company.

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Overall, this is further evidence that marijuana-based drugs can treat some kinds of pain, although maybe not all of them. I have to say, though, that I'm not sure that we needed a placebo-controlled trial to tell us that terminal cancer patients can benefit from medical marijuana. If someone's dying from cancer, I say let them use whatever the hell they want, if they find it helps them. Dying patients used to be given something called a Brompton cocktail, a mixture of drugs that would make Keith Richards jealous: heroin, cocaine, marijuana, chloroform, and gin, in the most popular variant.

And why not? There were no placebo-controlled trials proving that it worked, but it seemed to help, and even if it was just a placebo (which seems unlikely), placebo pain relief is still pain relief. I'm not saying that these kinds of trials aren't valuable, but I don't think we should demand cast-iron proof that medical marijuana works before making it available to people who are suffering. People are suffering now, and trials take time.

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Johnson JR, Burnell-Nugent M, Lossignol D, Ganae-Motan ED, Potts R, & Fallon MT (2009). Multicenter, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study of the Efficacy, Safety, and Tolerability of THC:CBD Extract and THC Extract in Patients With Intractable Cancer-Related Pain. Journal of pain and symptom management PMID: 19896326

Selvarajah D, Gandhi R, Emery CJ, & Tesfaye S (2009). A Randomised Placebo Controlled Double Blind Clinical Trial of Cannabis Based Medicinal Product (Sativex) in Painful Diabetic Neuropathy: Depression is a Major Confounding Factor. Diabetes care PMID: 19808912

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