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15 Articles in Volume 16, Issue #6
Osteoarthritis and Central Pain
Uncovering the Sources of Osteoarthritis Pain
The Synergistic Effects of Mood and Sleep on Arthritis Pain
Nonsurgical Rx of OA: Analyzing the Guidelines
Osteoarthritis Disability Is Often Underestimated By Rheumatologists
10 Pain Medication Myths
The Use of Medical Marijuana for Pain in Canada
6 Common Concerns Regarding Medical Marijuana
What Pain Specialists Need to Know About Medicinal Cannabis
Applying Kinesiology as a Multipronged Approach to Pain Management: Part 2
Practical Guide to Adding Recreation Therapy Into Pain Management
A Novel Treatment for Acute Complex Regional Pain Syndrome
Genetic Testing in High-Dose Opioid Patients
No More “Fifth Vital Sign”
Letters to the Editor: Disc Herniation, SCS, Arachnoiditis, Tapering Opioids

What Pain Specialists Need to Know About Medicinal Cannabis

An interview with Barth Wilsey, MD

A growing number of states have approved medical marijuana (cannabis) to treat a variety of conditions, including neuropathic pain, spasticity, and pediatric epilepsy. Despite the increasing popularity of these treatments, there’s been an absence of uniform standards and guidelines in place to help medical professionals navigate the rapidly changing landscape in the most effective way. As a result, many pain specialists are left grappling with a host of important issues when it comes to incorporating cannabis into a broader pain treatment strategy. Here is some insight from an experienced practitioner on treating pain with cannabis.

Q How did you get interested in studying medicinal cannabis?

Dr. Wilsey: In 1994, I was a pain research fellow at University of California, San Francisco (UCSF). As part of my duties, I worked in the UCSF Pain Clinic and wrote many prescriptions for chronic pain patients. Several patients informed me that prescription medications were ineffective and they preferred to use cannabis. They obtained the cannabis from cooperatives in Oakland, California.

This was 2 years prior to the passage of Proposition 215, the Compassionate Use Act of 1996.1 Several years later, after the California Legislature passed the Medical Marijuana Research Act of 1999,2 the UC Center for Medicinal Cannabis (CMCR) was established.3 With the CMCR’s assistance, I was able to obtain the requisite federal approvals from the Department of Health and Human Services (DHHS), Drug Enforcement Administration (DEA), Food and Drug Administration (FDA), and National Institute of Drug Abuse (NIDA). Subsequently, we performed 2 randomized, controlled crossover studies demonstrating the efficacy of medicinal cannabis in the treatment of neuropathic pain.4,5

Q  How can pain specialists understand some of the issues regarding medical cannabis?

Dr. Wilsey: My CMCR colleagues and I decided to use our collective experience studying cannabis to provide some guidance on this issue to other physicians.6 We borrowed concepts developed for the prescription of opioids—namely, the use of a written agreement to describe and minimize risks when discussing medicinal cannabis with patients. Intended to be printed and distributed to patients, this agreement was developed for patients to read at home, so they could get a clear understanding of the benefits and risks involved and query providers at subsequent visits if they have questions.

Q  Are most patients appropriate candidates for medicinal cannabis? And if not, can you explain what groups might not be a good fit for using this treatment?

Dr. Wilsey: When recommending cannabis to patients, pain specialists must recognize that some people will have an increased risk from harmful effects. Contraindications include pregnant women, individuals with coronary heart disease, and/or those with serious mental illness (eg, schizophrenia and bipolar disorder).

Q  What advice do you offer for pain specialists to guide patients in getting the therapeutic benefits for neuropathic pain from medicinal cannabis with minimal side effects?  

Dr. Wilsey: Pain physicians should recommend that patients use the lowest dose of delta-9-tetrahydrocannabinol (THC) that the patient finds to be effective. This is important not just to minimize the psychoactivity, but also to decrease cognitive impairment. We performed human laboratory experiments where participants received pain relief with only 1.3% delta-9-THC.5 There was very little of either psychoactivity or cognitive impairment at this dose level.

However, longer-term studies (weeks to months) are needed before we can conclude anything definitive concerning whether or not a dose this low would be effective over a long-term period. Yet it still makes sense to recommend that patients use the lowest dose available that provides pain relief so that side effects are minimized.

There is also a growing interest in using medicinal cannabis that contains cannabidiol (CBD) in addition to delta-9-THC. CBD can counteract some of the negative effects of delta-9-THC, such as psychoactivity, although such findings have not always been consistent. I expect that we will see more investigative work on the combination of these two cannabinoids in the future (See related article).

Q What should pain specialists know about any potential dangers to the lungs when people smoke cannabis?

Dr. Wilsey: Cannabis increases cough, sputum production, hyperinflation, and upper lobe emphysematous changes.7,8 Although regular cannabis smoking leads to bronchial epithelial ciliary loss and impairs the microbicidal function of alveolar macrophages, evidence is inconclusive regarding possible associated risks for lower respiratory tract infection.9

We also know that cannabis smoke contains carcinogens, but in several well-respected epidemiological studies, light or moderate use of cannabis did not seem to increase the risk of lung cancer or cancer of the upper airways. However, one study found that heavy use (defined as more than 50 times of use during the lifetime) doubled the risk of developing lung cancer over a 40-year timeframe.10 This is certainly important to keep in mind.

Q  Can you talk about some of the other compounds that exist in the oral form of medicinal cannabis and if they may be useful for people with neuropathic pain and other conditions?

Dr. Wilsey: There are several compounds in oral form currently approved by the FDA. For instance, dronabinol (Marinol), an oral form of delta-9-THC, is used to stimulate appetite, reduce nausea, and reduce pain. There’s also nabilone (Cesamet). Such pharmacologic oral preparations avoid harmful effects on the respiratory system. However, some experts believe that whole plant cannabis is superior to the FDA-approved oral compounds. As verification, these experts point out that oral delta-9 THC compounds have been on the market in the United States for many years and yet are not widely used.11 Presumably, patients favor whole plant cannabis because of its rapid onset and easy titratability.

Q Is using cannabis in a vaporized form a viable alternative for pain patients?

Dr. Wilsey: Cannabis vaporization is a method aimed at controlling irritating respiratory toxins by heating cannabis to a temperature where active cannabinoid vapors form, but below the point of combustion where smoke and associated toxins are produced. Vaporization has been shown to have similar pharmacokinetics to the inhalation of cannabis cigarettes.12

Q Preventing young people from having access is a big concern with medicinal cannabis. What should pain specialists know about this issue?

Dr. Wilsey: Cannabis is one of the most widely used illicit drugs among adolescents. All too often, they report obtaining cannabis from someone who uses medicinal cannabis. Patients must be warned to safeguard their supply of cannabis and prevent it from being diverted to children and adolescents (similar to recommendations for opioid medications). It is clear that youth who are under the influence of cannabis may suffer academically and, with continued use, drop out of high school or college. In some cases, this may be due to a loss of motivation.  

Q Can adults using medicinal cannabis also be at risk for losing motivation?

Dr. Wilsey: Whether a motivational syndrome in adults exists or not is still controversial; there are still too few studies to draw a conclusive answer. But medicinal cannabis patients who stop going to work or doing their chores need to talk to their doctor. This can indeed be a sign that the patient is losing motivation and perhaps becoming addicted to cannabis. If people begin to take cannabis with the intent of getting stoned rather than to relieve pain, this is also a sign that they need to speak with their physician.

Q Is withdrawal from medicinal cannabis a concern?

Dr. Wilsey:  People who use cannabis heavily can experience withdrawal when they stop abruptly. The syndrome can last for up to 2 weeks. Among other things, the signs of withdrawal include anger, sweating, restlessness, interrupted sleep, reduced appetite, stomach pain, nightmares, and weight loss. Re-administering and tapering the cannabis slowly over time can help suppress these symptoms.13

Q What are some other safety and work-related issues that pain specialists should consider with medicinal cannabis?

Dr. Wilsey:  The National Highway Traffic Safety Administration points out that cannabis has been shown to impair performance on driving simulator tasks and on open and closed driving courses for up to approximately 3 hours.14 Furthermore, mixing alcohol and marijuana may dramatically produce effects greater than either drug on its own.  It’s also worth noting that when people test positive for marijuana in their urine, they can lose their jobs. There are currently no laws protecting medicinal cannabis patients at this time, and courts usually decide in favor of employers.

Q What about using opioids and marijuana [cannabis] together?

Dr. Wilsey: Patients should be counseled to stop or lessen use of other drugs that can impact the central nervous system, including opioids, sedative-hypnotics, and alcohol, while using medical cannabis. That being said, there is a study that demonstrates that when opioids and cannabis are taken together, the effect of the opioid is augmented.15 Another epidemiologic study has shown that in states where medicinal cannabis is legal, there is a lower rate of inadvertent overdoses from opioids.16

Q How can pain specialists learn more about this topic and how can they access a copy of the medical cannabis agreement you developed?

Dr. Wilsey:  Pain specialists can refer to an article published by several faculty from the UC Center for Medicinal Cannabis Research in The Clinical Journal of Pain in December 2015.6 There is an appendix that provides the tenets of the written agreement (medical marijuana contract) I mentioned earlier. Physicians can copy this and keep it in their files. When a patient wants to use medicinal cannabis, pain management physicians can retrieve the agreement and go over it with the patient.


Last updated on: February 26, 2019
Continue Reading:
Applying Kinesiology as a Multipronged Approach to Pain Management: Part 2

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