CBD: What physicians need to know about it


Cannabidiol is a derivative of marijuana that is sold everywhere from medical marijuana stores to health food markets to gas stations. While this chemical is derived from marijuana plants, it can be sold in many states as a supplement and is largely unregulated. The ubiquity of cannabidiol (CBD) and its potential benefits means that doctors need to be able to counsel patients about what we know, what we don’t, and how to use it safely. For conditions such as chronic pain and addiction, where we have few safe and effective alternatives, CBD may be reasonable to recommend.

Dr. Elisabeth Poorman, University of Washington, Seattle

Dr. Elisabeth Poorman

To find out what physicians need to know about CBD, Elisabeth Poorman, MD, a general internist at a University of Washington neighborhood clinic in Kent and member of the editorial advisory board of Internal Medicine News, interviewed Peter Grinspoon, MD, who provides free consultation to primary care patients on the benefits and risks of using various forms of cannabis, including CBD. Dr. Grinspoon is an internist at Massachusetts General Hospital Chelsea Healthcare Center and is an instructor at Harvard Medical School, Boston. He has contributed to the Harvard Health Blog on the topic of medical marijuana, delivered grand rounds on cannabis at Massachusetts General Hospital, and lectured at the American College of Physicians. Dr. Grinspoon is also medical director for Galenas, a medical marijuana company.

Dr. Grinspoon is the son of Lester Grinspoon, MD, associate professor emeritus of psychiatry at Harvard Medical School, who researched the medicinal legitimacy of marijuana prohibition and has authored books on the medical benefits of marijuana.

Dr. Poorman queried Dr. Peter Grinspoon about his experiences treating patients with CBD and his knowledge of CBD’s efficacy for various medical conditions. Below are excerpts from that conversation.

Dr. Poorman: How do you explain the difference between THC and CBD to patients?

Dr. Grinspoon: Cannabis contains at least a hundred different chemicals called cannabinoids, of which tetrahydrocannabinol (THC) and CBD are the most prevalent. THC is the one that gets you high and can be used recreationally and medically. The CBD molecule is not intoxicating, and people use it for a variety of medical purposes, most commonly to treat anxiety, insomnia, and pain.

Dr. Poorman: There are a lot of gaps in what we now about CBD’s potential benefits. Why don’t we know more?

Dr. Grinspoon: CBD has no abuse liability according to the World Health Organization, but because it is a cannabinoid, it is still technically a schedule I substance under the Controlled Substances Act, and that makes it difficult to study.

Dr. Poorman: What kinds of conditions can CBD treat?

Dr. Grinspoon: In anxiety, the enthusiasm has outpaced the science; there’s no question about that. And most of the studies have done in animals. That said, some studies have shown that CBD helps treat components of anxiety, like public speaking. Unlike THC, it is nonintoxicating and non–habit forming. But we don’t have the wealth of randomized controlled trials that we have for official psychiatric medications.

CBD’s benefits have been most extensively studied in pediatric epilepsy. The one Food and Drug Administration–approved drug derived from cannabis is Epidiolex, used to treat rare forms of childhood epilepsy. There is some evidence that as an adjunct, it can be used for glioblastoma multiforme in patients receiving other appropriate therapy. There is also some preliminary evidence that it can be used for addiction, including to opioids, cannabis, tobacco, and stimulants.

Most of the evidence for using CBD in chronic pain comes from animal studies, including a study published in the European Journal of Pain in 2016. Among my patients to whom I have suggested CBD for chronic pain, a few have noticed great benefit, a few have noticed some benefit, and a lot have noticed no benefit. For those who have said they noticed benefit it is unclear whether that benefit was just the placebo effect.

In insomnia, I usually have them take CBD under the tongue half an hour time before bedtime, or if it’s an edible, an hour before bedtime. I start with a lower dose and slowly try higher doses. I also encourage them to do the other sleep hygiene things, like no screens, increasing exercise, and decreasing caffeine. It seems that CBD helps them fall asleep, though it’s hard to know if it’s the CBD or the fact that they have started taking something, and have simultaneously made various lifestyle changes.

Dr. Poorman: Can CBD interfere with your normal sleep architecture, the way benzodiazepines and Benadryl can?

Dr. Grinspoon: We know that THC affects your sleep architecture and affects what percentage of REM sleep you have. But I don’t know if the effects of CBD on sleep architecture have been studied.

Dr. Poorman: What harms do you counsel patients about when discussing CBD?

Dr. Grinspoon: There are four main harms. The first is the price. It’s overpriced, and the doses are very low. In most animal studies, the doses are about 20 milligrams per kilogram of weight. And you go to the market, and it’s like a dollar for a hundredth of that.

Number two is that it’s not regulated; it’s a supplement. A few years ago, the government tested a bunch of samples of CBD, and some didn’t actually contain CBD, some didn’t have the right amount; and worse, some contained THC that had not been disclosed in the packaging. So you can’t just go to a roadside gas station and assume that if you buy CBD, it’s actually that. You want a place that has a certificate of assurance. Make sure third-party testing was done, including testing for pesticides and other heavy metals.

The third thing is drug interactions. It affects the body like grapefruit and inhibits the cytochrome P450 system. The medications doctors should be most concerned about are blood thinners like Coumadin. And if you’re on blood thinners, you definitely want to tell your doctor that you are on CBD and he or she might want to check your blood levels more frequently than they usually do.

The fourth concern is liver inflammation. In the childhood epilepsy studies, a bump in some liver enzymes was seen, although I haven’t heard of any clinically significant cases of chemical hepatitis related to CBD. But if someone has liver disease you want to keep an eye on their liver enzymes.

Dr. Poorman: What methods of ingestion do you recommend or not recommend?

Dr. Grinspoon: It’s basically trial and error, but I usually recommend oral form. If people feel comfortable taking a gummy bear, or a pill, I’m not particular about that. If the product being taken contains less than 0.3% THC, it won’t get you high.

The topical form probably works better for treating chronic pain if it contains some THC, suggests a review article published in the Cleveland Clinic Journal of Medicine. Topical THC is nonintoxicating, unless you managed to sit in a bathtub for 8 hours after applying it.

I don’t recommend smoking CBD, and right now, I don’t recommend vaping anything.

If people have severe pain, like moderately severe arthritis, CBD may not be enough, whereas medical cannabis with THC could help, a report suggests.

Dr. Poorman: Do you ever encourage patients to stop using CBD products?

Dr. Grinspoon: I work in a low-income area, and my patients don’t have a ton of disposable income. If it’s not working, I worry about the expense.

Dr. Poorman: The CBD industry is growing quickly. What changes are you seeing in what products are out there, and what changes would you like to see?

Dr. Grinspoon: CBD is being put in everything, and it’s comical. On the one hand, you can say if people want to waste their money on a CBD emitting pillowcase, that’s fine. On the other hand, you can say that certainly seems like misleading advertising, because a CBD emitting pillowcase isn’t going to help you sleep any better.

I think the purported benefits are far beyond what we can say scientifically. We do know that CBD has anti-inflammatory characteristics. But that doesn’t mean that putting CBD in all skin products is good for your skin. It’s bad for your pocketbook, though. I would like there to be less of a gap between the claims and the science.

Dr. Elisabeth Poorman has no conflicts to disclose.

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