If you’ve visited a store that sells health and beauty products lately, you may have noticed that products containing CBD, or cannabidiol, seem to be all the rage. Oil, chocolate, supplements, even carbonated beverages, are filling up shelves—enticing shoppers with claims that using one of these products will cure insomnia, alleviate anxiety, reduce inflammation, or treat PTSD.
And shoppers are buying it, so to speak—one recent report indicated that CBD sales are expected to hit $16 billion by 2026, up from just over $1 billion in 2018. But what exactly is CBD, and is it safe for people who are using prescription medications? Before using it, it’s important to learn about the potential CBD drug interactions.
Is CBD marijuana?
While CBD is one of the active ingredients in marijuana, using CBD itself will not get you high (the component that does that is called tetrahydrocannabinol, or THC). CBD is really just a molecule within the hemp variety of the cannabis plant, and there is at least some anecdotal evidence and preliminary research suggesting that the extraction created from this molecule has some health benefits.
CBD is thought to act on certain receptors in your brain and other parts of the body, in ways that could relieve pain, or help certain health conditions, like childhood seizure disorders. However, as with any “natural” product, the fact that it comes from plants doesn’t automatically render it innocuous. For some people, particularly those taking certain prescription medications, using CBD is risky. It has anticoagulant effects that can thin blood; it can also modestly lower blood pressure. These effects could be dangerous for people with certain medical conditions.
“Herbal products are drugs,” says Rita Alloway, Pharm.D., research professor of nephrology at the University of Cincinnati College of Medicine. “Just because [something] is herbal … doesn’t mean it can’t interact with any of the pharmaceutically manufactured drugs that you may be taking.”
Does CBD interact with medications?
Case in point: tacrolimus, an immunosuppressive medication used to prevent organ rejection in patients who have had heart, liver, or kidney transplants. CBD interferes with the metabolism of tacrolimus, according to research conducted by Dr. Alloway, who specializes in post-transplant immunosuppression. And because tacrolimus is a narrow therapeutic index drug (meaning the window between efficacy and toxicity is very small), this interference can lead to clinically significant negative outcomes (such as kidney problems or organ rejection), she says.
Are the concentrations in commercially available CBD high enough to cause this interaction? The evidence doesn’t really say one way or another. Dr. Alloway’s research involved a high dosage of CBD that wouldn’t be found in a retail product. However, it “highlights that a drug interaction is there,” she says. Plus, tacrolimus is metabolized in the body by a group of enzymes called cytochrome P450 and CBD is a known inhibitor of this process. What does that mean? If CBD inhibits the metabolism of tacrolimus, the patient can end up with too-high levels of tacrolimus in the body. In light of this, she urges anyone taking tacrolimus to speak with their transplant team before using CBD. Don’t get your hopes up, though—using herbal remedies, particularly those with potential interactions, is generally frowned upon by doctors looking after transplant recipients (including Dr. Alloway).
As for other drugs, well, most haven’t been studied yet. There is preliminary evidence that CBD could have a similar effect to grapefruit juice, impairing how your body metabolizes drugs, and raising serum levels of those medications in your body. And, because cytochrome P450 is responsible for the metabolism of numerous medications, proceed with caution before mixing any prescription pharmaceutical with CBD, Dr. Alloway says.
How about CBD’s therapeutic benefits?
Despite the not-so-great news about CBD for patients using tacrolimus, for some people, CBD is actually life-changing in a positive way. In 2018, for example, the CBD-derived medication Epidiolex received FDA approval for the treatment of Lennox-Gastaut syndrome and Dravet syndrome, two very rare and very severe forms of epilepsy.
But claims that CBD aids in the treatment of certain mental health and psychiatric conditions, don’t pass muster, says Roger McIntyre, MD, professor of psychiatry and pharmacology at the University of Toronto.
“There is no role right now for CBD in managing mental disorders that I [treat], such as depression, bipolar disorder … anxiety and ADHD,” he says. “We just don’t have the evidence that supports [it].”
Furthermore, most prescription medications used to manage these conditions are metabolized by cytochrome P450, making it entirely possible that CBD could interfere with—rather than enhance—treatment.
Dr. McIntrye, who co-authored a 2018 study that concluded that healthcare providers need more information about drug-drug interactions with CBD and psychotropic medication, says much of the information out there is confusing and contradictory. Therefore, he echoes Dr. Alloway’s statement that it is absolutely prudent that patients clear the use of CBD with their doctor before giving it a go.
“[The provider] knows the individual and knows what other treatments they may or may not be taking,” Dr. McIntyre explains. “They have a panoramic view of the patient’s medications, and would have [a better idea] of whether the patient is taking another medication that may have an interaction.”