A scientific panel discussion and multi-faceted look at cannabinoids in pain management was one of the more well-attended sessions at the New York State Society of Anesthesiologists' Post-Graduate Assembly (PGA) in December 2016. As of the end of 2016, state legislatures in just over half of the United States had approved at least some form of marijuana use for medical purposes with a physician's prescription, and a handful more were expected to consider such laws during 2017.

Will DEA Registration Put Opioid Prescribers At Risk?

For pain physicians who are registered with the US Drug Enforcement Administration to prescribe controlled substances, however, there is still a pressing concern: Even if they prescribe medical marijuana in a state that allows it, their DEA registration is a federal status. Will they be vulnerable to sanctions by the US DEA? Even if prescribing marijuana makes them more vulnerable to investigation by the DEA, it can have a chilling effect.

Under federal law, there is no such thing as medical marijuana-there is only marijuana, a Schedule I substance, meaning it is addictive and serves no medical purpose in the eyes of federal law.

Although at least 26 states have passed laws allowing physicians to prescribe marijuana for certain patients, marijuana remains illegal in federal court. There have been challenges to this in the past, mostly during President George W. Bush's administration. President Barack Obama's administration did not prosecute medical marijuana cases that did not violate the state laws where they exist.

For the cases that came to the US Supreme Court during the Bush years, however, the court ruled against any attempts to legalize medical marijuana.

Know the Science and the Law-Even if You Don't Prescribe

Whether or not a physician is willing to prescribe marijuana, all pain practitioners should become aware of the medical and scientific research behind these substances, their interaction with traditional prescription and over-the-counter drugs, and their potential long-term side measurable effects on the human brain, said experts on the scientific panel in New York in December.

Presenting the body of evidence on cannabinoids were:

* Sudhir Diwan, MD, DABIPP, clinical associate professor at Albert Einstein College of Medicine and executive director of Manhattan Spine & Pain Medicine, who focused on literature related to cannabinoids and chronic pain.

* Oscar DeLeon Casasola, MD, professor and chief of pain medicine at Roswell Park Cancer Institute and professor and vice-chair for clinical affairs in the Department of Anesthesiology at the Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, who focused on literature indicating some long-term effects on the brain from use of marijuana.

Diwan gave an overview of existing literature, but he emphasized that there is still a shortage of high-quality controlled and randomized studies on medical marijuana. Still, he said, in states where it is legal, pain practices are bound to see patients who have been or could still be using medical marijuana or self-medicating with it.

Pain Practitioners Must Learn About Cannabinoids

"You should at least learn as much as you can about it," Diwan told those present, who attended from all over the country and abroad. Considering the disastrous way in which opioid prescribing led to an unintended rise in deaths from overdose and abuse before the medical community fully understood the risks, he said, practitioners owe it to their patients to proactively learn as much as they can about a drug that may see increased prescribing and use in the next several years.

"The legalization of marijuana use, recreational and/or medical, has almost forced us to learn everything about marijuana," Diwan said. "Does it have analgesic effects? Is it safe? How would affect the prescriptions of opioids? Urine toxicology screen with positive marijuana: Now what? Would you discharge the patient from practice? What about concurrent use of opioids? Do we have enough knowledge of interactions?"

Diwan told the group that use of marijuana for headache and back pain has been documented as early as the 6th Century, with references in the medical literature since the mid-1800s. However, it was removed from medical use in the 1940s because of increased scrutinization over psychoactive and recreational use.

Much of the science behind medical marijuana has been to find ways to maximize the therapeutic benefits while removing the psychoactive properties that make it more appealing for recreational use and more addictive.

Two Main Cannabinoids Being Studied

The marijuana plant actually contains more than 113 identified cannabinoids. Of these, tetrahydrocannabinol (THC) is responsible for the psychoactive properties, while cannabidiol (CBD) has been shown to have medical application, but without the psychoactive properties.

Diwan wrote in his presentation abstract: "The THC has psychoactive, anti-inflammatory, neuro-protective, antinausea, and analgesic actions. The CBD is non-psychoactive, with no significant affinity for CB1 and CB2 receptors. It blocks formation of 11-OH-THC (the most psychoactive metabolite of THC). It is a potent CYP450 3A1 inhibitor and mitigates the side effects of THC (anxiety, dysphoria, panic reactions, and paranoia) while improving THC's therapeutic activity."

Brain Studies Indicate Risk with Long-Term Marijuana Use

While Diwan focused his presentation on some of the potential benefits that medical marijuana may provide for chronic pain patients, DeLeon presented data from studies that have found evidence that marijuana may negatively affect function even if it does provide some relief from pain. Physicians, he said, will need to be vigilant about considering the drug's effect on function in order to help patients weigh the risks versus the benefits.

DeLeon's talk was entitled, "Would You Use Marijuana If You Knew This?"

"This is an important question, because with the approval of marijuana use, we may be facing another addiction epidemic," DeLeon said.

His data included studies showing incentive-sensitization models that suggest that alterations in the brain's reward system are, at least in part, related to cannabinoid use. Data have shown sensitization of mesocorticolimbic regions and disruption of natural reward processes after marijuana use. These pathways play a central role in addiction.

DeLeon presented data from studies showing changes in both the gray and white matter brain structure. Adolescents are particularly vulnerable, the data show, demonstrating more deficits in effortful processing and complex cognition.

He also referred to studies indicating marijuana's anti-inflammatory and antioxidant properties may also lead to neural changes, including greater myelination and possible neurotoxicity.

"Whether abstinence reverses such effects remains unknown," DeLeon said.

Further Reading

Articles Diwan cited in his abstract include: