Cannabis for chronic pain: Are we there yet?

Originally posted on August 31, 2010 –PalMD

Marijuana is pretty popular stuff, and for good reason.  It is a potent drug, capable of both making someone feel good and of reinforcing dependence pathways in the brain.  Cannabis has been lauded for its ability to treat nearly any unpleasant symptom (except perhaps dry mouth), but so far evidence other than the anecdotal has been meager.

One of the areas where research has been a bit promising is in the treatment of certain types of nerve pain.  Small studies have shown some possible benefit in certain groups of patients, but robust studies are lacking.  In the U.S., this is certainly due at least in part to restrictions on cannabis research, but only in part.

Still, chronic nerve pain is an important problem, with imperfect treatments.  Opiates such as morphine are effective but come with significant side-effects.  Some anti-seizure medications such as gabapentin and pregabalin have shown some promise, but they are relatively expensive (although the price on gabapentin is dropping) and only somewhat effective.  Finding effective drugs, to be used either alone or in combinations, would help people suffering from a frustrating and sometimes disabling problem.

The Canadian Medical Association Journal recently released a study on cannabis.  The study focused on smoked cannabis in a subset of patients with chronic nerve pain.  Cannabis and its active ingredients are available in many forms, including oral mixtures of cannabis extract and THC alone.  The authors don’t give a specific justification for the use of traditional pot-smoking, but the editorial that accompanies the piece suggests that:

It’s good to see the trial of smoked cannabis in neuropathic pain reported by Ware and colleagues because smoking is the most common way in which patients try this drug.

I hope that this isn’t the justification intended by the authors.  This may be obvious to most readers, but choosing a route of delivery based on “what they do on the street” is not a terribly clever thing to do.  Even raw cannabis can be delivered by (probably) safer inhaled means such as vaporization (and they do mention vaporization at the end of the paper).

In any case, the study was, in some respects, well-designed.  They appeared to have a good placebo control, which is no small feat in a study of smoked cannabis.  And they did find some modest improvement in pain scores, and noted that this reduction was dose-dependent—the more potent the weed, the lower the post-treatment pain score.  But in total, the evidence isn’t terribly convincing.

The study was very small, and the authors admit that their results were modest, especially when compared to already-available medications.  They attempt to minimize this by noting that the patients chosen had already failed conventional therapy, although the study design does not suggest this to be strictly the case.

While this study gives us reason to continue to look at cannabis, it does not give convincing evidence that cannabis improves upon currently available drugs in regards to safety and efficacy.

References

Mark A. Ware MBBS, Tongtong Wang PhD, Stan Shapiro PhD, Ann Robinson RN, Thierry Ducruet MSc,, & Thao Huynh MD, Ann Gamsa PhD, Gary J. Bennett PhD, Jean-Paul Collet MD PhD (2010). Smoked cannabis for chronic neuropathic pain: a randomized controlled trial (Early e-release) Canadian Medical Association Journal : 10.1503/cmaj.091414

14 Comments

  1. “While this study gives us reason to continue to look at cannabis, it does not give convincing evidence that cannabis improves on currently available drugs in regards to safety and efficacy.”

    I don’t understand this- why does it need to improve? The “every patient is an experiment” post shows the value of having many different medicines available for one condition.

    The drug war isn’t going anywhere, it is too useful. The hoops that labs have to jump through just to *test* for drugs of abuse is crazy enough, I can just imagine what people who want to do serious research have to go through. The DEA has all kinds of obstacles set up.

  2. Thanks for your analysis of this study. I completely agree about the comments regarding smoking. Many of the labels produced for medical cannabis that I have seen even include the information that vaporization is recommended. And of course, ingestion is also a popular form of consumption that is most likely a lot safer than inhaling at all.

    I’m curious about your opinion on something (and yes, I really am curious, not giving you grief). In some illnesses or syndromes, like “garbage-can diagnoses” such as CFS and fibromyalgia, the pain and malaise are by definition not well understood, as well as fluctuate wildly from patient to patient. How could one design a good clinical study for use of cannabis with those conditions? It seems like you’d have to do a different study for a number of different patient cohorts (those with mostly post-viral symptoms, those with neurological symptoms, etc.).

  3. aidel

     /  August 31, 2010

    Unfortunately, the link to the actual paper didn’t work (?). I would like to learn more about this subject, so additional links to other studies would be great, if any are available. I can think of plenty of reasons that marijuana (even smoked) might be a better treatment option than opioids. My understanding is that if gabepentin works at all (for many it doesn’t), the degree of pain relief is often inadequate. What about marinol? And does marijuana really address the issue of pain or just make the patient less focused on the pain? (In other words: does it really hurt less or is it that it hurts, but you just don’t care as much?) The distinction is not insignificant. Chronic pain WILL drive you crazy.

  4. Most studies do not compare different forms of cannabis and don’t compare cannabis to other pain relievers. Good studies are definitely lacking. As I’ve written before, there is good plausibility behind many of these hypotheses, but as yet they are not tested enough.

  5. Nathan Myers

     /  August 31, 2010

    It’s probably hard to conduct a trial in which none of the participants are self-medicating with cannabis.

  6. Jillian Galloway

     /  August 31, 2010

    $113 billion is spent on marijuana every year in the U.S., and because of the prohibition *every* dollar of it goes straight into the hands of criminals. Far from preventing people from using marijuana, the prohibition instead creates zero legal supply amid massive and unrelenting demand.

    According to the ONDCP, at least sixty percent of Mexican drug cartel money comes from selling marijuana in the U.S., they protect this revenue by brutally torturing, murdering and dismembering thousands of innocent people.

    If we can STOP people using marijuana then we need to do so now, but if we can’t then we need to legalize the production and sale of marijuana to adults with after-tax prices set too low for the cartels to match. One way or another, we have to force the cartels out of the marijuana market and eliminate their highly lucrative marijuana incomes – no business can withstand the loss of two-thirds of its revenue!

    To date, the cartels have amassed more than 100,000 “foot soldiers” and operate in 230 U.S. cities, and the longer they’re able to exploit the prohibition the more powerful they’ll get and the more our own personal security will be put at risk.

  7. Vicki

     /  August 31, 2010

    Nathan–

    I know at least two chronic pain patients who aren’t self-medicating with cannabis. (One does use a variety of things like scent, though that might be called distraction rather than self-medication.) “At least two” because I know another with whom I haven’t discussed this.

    I suspect, though, that at least one of them wouldn’t be eager to try it even under medical supervision: she dislikes alcohol and has told me that she doesn’t understand why people like being drunk/stoned.

  8. The current study attempted to control for current users, ie there were no current users in the study.

  9. Nathan Myers

     /  August 31, 2010

    1. Controlling for current users by removing them biases the results, by filtering out people who have already found that cannabis helps them. Indeed, anybody who is already satisfied with it, and can get it, wouldn’t be motivated to participate at all. (People using but not satisfied are likely to miss the signup deadline.)

    2. I was speaking of trials more generally. How carefully do trials of any given substance track users of cannabis? If they are excluded, then any interactions won’t register. Certainly once it starts being subscribed, it will start to mix with THC in patients. Didn’t we learn anything about exclusion from thalidomide?

  10. Nathan Myers

     /  August 31, 2010

    s/subscribed/prescribed/

  11. OleanderTea

     /  August 31, 2010

    @ Nathan:

    I’m a chronic pain patient who is not self-medicating with cannibas, at least in part because my pain management contract includes monthly drug testing. Oh, and I can’t even jaywalk without getting caught.

    But here’s the thing: cannibas will make you not care that you hurt like a bastard. I don’t really see a problem with that.

  12. Kipper

     /  August 31, 2010

    Have you seen the 20/20 clip on medical marijuana for kids? I know there are worse things out there (chelation, etc.), but I was still somewhat shocked.

  13. Gareth

     /  October 11, 2010

    You Yanks are funny

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