Medical Marijuana and Chronic Pain: Considerations for Use within States That Have Laws in Place


As of March 2015, 23 states and the District of Columbia had medical marijuana laws in place. A recent published study in the Journal of the American Medical Association (JAMA) by Kevin P Hill, MD, of Harvard Medical School reviewed the pharmacology, indications and laws related to medical marijuana use, with emphasis on its use in treating chronic pain

Hill reviewed 28 randomized clinical trials of cannabinoids as pharmacotherapy for indications other than those for the two U.S. Food and Drug Administration (FDA)-approved cannabinoids, dronabinol and nabilone. What he found was that the use of marijuana for chronic pain, neuropathic pain, and spasticity due to multiple sclerosis was supported by high-quality evidence. According to Hill, several of those trials had positive results, suggesting that marijuana or cannabinoids may be efficacious for these indications. 

By R.L. Wynn

The Hill study

Hill, K.P. “Medical marijuana for the treatment of chronic pain and other medical and psychiatric problems. A clinical review.” JAMA 2015; 313(24) 2474-2483.

The paper was inspired by a case study regarding a 60-year-old man with a long history of chronic low back pain refractory to multiple procedures and medications. The patient began using medical marijuana after receiving certification from a local specialty medical marijuana clinic. The patient indicated that the marijuana improved his pain control, and he approached his primary care physician about continuing the use of marijuana for his pain.

This medical case prompted Hill to search the literature on medical marijuana from 1948 to March 2015 on MEDLINE, using the search terms cannabis, cannabinoids and tetrahydrocannabinol. A total of 74 articles were reviewed. There were no meta-analyses on the topic of medical marijuana and there were three systematic reviews. The main emphasis for inspection of the reviews was in randomized clinical trials.

Medical marijuana defined

Medical marijuana may be identical in form to recreational marijuana; it consists of the dried material from the cannabis plant consisting of tetrahydrocannabinol (THC), cannabidiol, and other cannabinoids. When purchased from dispensaries, it comes in a variety of preparations, or it can be grown by patients.  It is interesting to note that it is not dispensed by pharmacies because of its status as a federally illegal drug.

Cannabis preparations available from state-approved medical marijuana dispensaries:

  • Marijuana – The dried plant product consisting of leaves, stems, and flowers; typically smoked or vaporized.
  • Hashish – Concentrated resin cake that is ingested or smoked.
  • Tincture – Cannabinoid liquid extracted from the plant; it is consumed sublingually.
  • Hashish oil – The oil obtained from the cannabis plant by solvent extraction; usually smoked or inhaled.
  • Infusion – The plant material mixed with non-volatile oily substances, such as butter or cooking oil, and ingested.

Hill inspected published data from more than 40 clinical trials of marijuana and cannabinoids. The strongest evidence existed for the use of marijuana and cannabinoids for the treatment of chronic pain, neuropathic pain, and spasticity associated with multiple sclerosis. There were six trials (325 patients) examining chronic pain, six trials (396 patients) examining neuropathic pain, and 12 trails (1,600 patients) that examined spasticity associated with multiple sclerosis. The use of marijuana for these conditions was supported by high-quality evidence, which was defined as multiple randomized, controlled clinical trials with positive results. The evidence supporting the use of marijuana and cannabinoids for other conditions – meaning conditions other than the three selected by Hill and those FDA-approved indications for nabilone (appetite stimulation in wasting illness) and dronabinol (nausea and vomiting associated with chemotherapy) – was either equivocal or weak.

Medical marijuana certification for treatment

Determining which patients may be candidates for medical marijuana treatment can be complex. Under federal law, marijuana is illegal, is classified as Schedule I under the Controlled Substances Act, and therefore cannot be prescribed by physicians. As a result, a physician could only “certify” its use. Thus, a certification process has been developed.

Patients who are to be certified for marijuana treatment should have a condition known to be responsive to marijuana based on high-quality evidence. For example, chronic pain would be such a condition. One scenario would be that the patient presents to his primary care physician seeking medical marijuana certification. In this situation, the certification would be written by a physician who has assessed the patient with the understanding of the patient’s condition requiring treatment. 

According to Hill, the U.S. Department of Justice has stated that it plans to leave the issue of medical marijuana to the states and not enforce the federal statute. Medical marijuana certification must state the specific medical condition for which the physician believed marijuana would be an effective treatment, and in some states, the certification has to indicate the recommend amount of marijuana needed to treat the condition.

Hill cited the state of Massachusetts as an example of how this would work. The physician would state the medical condition for which she is certifying treatment with medical marijuana as well as a recommended amount per 60-day period. The amount would be estimated based on the route of administration and the anticipated number of treatments per day. The dispensary then provides advice to the patient on which marijuana species or strain to purchase, dosing, and instructions on how to take it. After the patient begins the course of marijuana treatment, follow-up with the physician should occur, perhaps within a month’s time, with additional telephone contact as necessary. 

Adverse effects would be one of the reasons for the follow-up. The acute adverse effects of marijuana include impaired short-term memory, impaired motor coordination, and impaired judgment. This is especially relevant for driving, as marijuana use has been shown to double the risk of involvement in a motor vehicle crash.

Also, marijuana is potentially addictive. And regular use is associated with an increased risk of anxiety, depression, and psychotic illness. Hill indicates that marijuana can worsen the courses of these disorders.

The candidate for medical marijuana should have:

  1. A medical condition shown to be responsive to treatment. Currently those conditions are nausea and vomiting associated with cancer chemotherapy, anorexia from wasting illness like AIDS, chronic pain, neuropathic pain, and spasticity associated with multiple sclerosis
  2. Multiple failed treatments of first- and second-line pharmacotherapies for the condition being addressed
  3. No psychotic disorder, anxiety disorder, or unstable mood disorder
  4. Residency in a state with medical marijuana laws and meets the requirements of those laws

Another view

An editorial in the same issue of JAMA makes the point that, “if the states’ initiative to legalize medical marijuana is merely a veiled step toward allowing access to recreational marijuana, then the medical community should be left out of the process, and instead marijuana should be decriminalized.”

It can be accessed at:

D’Souza, D.C.; Ranganathan, M. “Medical marijuana. Is the cart before the horse?” JAMA 2015; 313(24): 2431-32.

The editorial goes on to note that, the way the process is explained, legal implications for the physician certifying patients for medical marijuana remain unclear, given the differences between the views of state versus federal government. The prescription, supply, or sale of marijuana is illegal under federal law, therefore, it is not known to what extent a physician who certifies a patient for medical marijuana may be liable for outcomes due to adverse reactions, such as motor vehicle crashes. Also it is not known if malpractice insurance will cover liability attributed to those physicians certifying medical marijuana use.

The editorial concluded that evidence justifying marijuana use or medical conditions will require more rigorous clinical trials to test short- and long-term efficacy and safety.   

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