Medical Marijuana for Pain? Many Questions Remain

Data are needed, and may be forthcoming as more registries like those launched this week in Quebec are launched.

PALM SPRINGS, Calif. — Healthcare providers specializing in pain management should become better versed on the existing scientific knowledge on the benefits and limitations of medical marijuana for chronic pain to more effectively counsel their patients. 


“We’re at this point where we have both scientific and population impetus to investigate this and it’s up to us to figure it out,” Mark Ware, MD, executive director of the Canadian Consortium for the Investigation of Cannabinoids and director of clinical research at the Alan Edwards Pain Management Unit at McGill University Health Center, said during a plenary session at the 2015 American Pain Society Meeting

“Even though there are no efficacy and safety data from large controlled clinical trials, doctors should learn about the plant itself and its myriad active ingredients by reviewing the scientific literature, understanding local legal issues and potential liability, and weighing the risks and benefits vs. other analgesics, including opioids,” Ware said. 

To date, about 15 trials of medical cannibinoids have been conducted worldwide, with findings indicating effectiveness in reducing pain from cancer, diabetes, fibromyalgia, and neuropathy. 

Currently, there are two FDA-approved cannabinoid medications — dronabinal and nabilone — with indications for controlling nausea and vomiting related to chemotherapy and for treating anorexia in patients with HIV. 

But several research gaps exist, as well as challenges to conducting pain studies involving marijuana. “With legalization of medical marijuana in more than 20 U.S. states, widespread access will yield more reports that need to be evaluated,” said Ware. 

Questions remain about whether it will be necessary to conduct clinical trials for every potential pain indication that could be treated with marijuana, and who best to back such studies financially. 

Another challenge to conducting large, phase-3 clinical trials include lack of standardization in cannibinoid products. “Plants grown in Colorado and other legalization states could be different, so when talking about cannabis in various states, there could be a variety of compounds,” Ware said. 

One area that’s not up for debate — the clear need for research to determine whether smoking is a safe route of administration compared with oral dosing. The majority of marijuana currently available as medicine is equivalent in quality and may carry the same health risks as marijuana sold on the street, according to the National Institute on Drug Abuse.

“There are safety concerns about the molecule itself, and studies of recreational marijuana users show the drug can affect the brain and lungs,” Ware said. “Much of what we know about medical marijuana is anecdotal, so the challenge is to recognize that patients who say they get pain relief by self medicating […] may be right, and move forward in conducting more scientific studies to better understand its analgesic benefits and overall safety.”

Ware said during the discussion that some of this data may be forthcoming, as just this week, the Quebec Cannabis Registry was launched. He said this program will follow patients who receive medical cannabis legally and will follow them over time, so hopefully he said “we can watch this and provide more long-term data.” 


  1. Ware M. Plenary Session. Presented at: APS 2015. March 13-16, 2015. Palm Springs, California.