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.
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).
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.
Does CBD interact with medications?
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.
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.
“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].”
“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.”
Similarly, a study investigating the potential ADEs and DDIs the researchers highlighted that medical CBD users under clinical supervision should be screened for potential DDIs and ADEs between CBD, other pharmacotherapies, and their underlying conditions. They also recommended that an increase in awareness is needed among the lay public who are recreational or consumer CBD users. Similarly, healthcare providers should also be made aware of the potential for DDIs and ADEs with CBD and strategically prescribe and manage patient regimens while also considering patient desires for complementary or alternative therapies.
The future of health
In another study investigating the interactions between CBD and commonly used anti-epileptic drugs, concluded that, although serum levels of the drugs topiramate, rufinamide, and N‐desmethylclobazam were found when use in conjunction with and increased CBD dosages. However, all changes were within the accepted therapeutic range but did underscore the importance of monitoring serum AED levels and LFTs during treatment with CBD.
CBD and anticancer agents
However, there are certain substances that have the ability to affect the way in which the CYP system processes compounds such as CBD that cause certain drugs to metabolize faster or slower than what they would normally have done.
For instance, any therapeutic compound that is metabolized by the CYP system has the potential of being affected by CBD. One indication that your medicine might be metabolized by the CYP system is if your pharmacist told you not to eat grapefruit, or watercress or use St. John’s Wort or goldenseal supplements. However, this is by no means a solid test and you should always check with your pharmacist of doctor first (more on that later).
There are also other medications known as “prodrugs” that first need to be metabolized into its therapeutic compounds as opposed to being a therapeutic compound in and of itself (like most medications). In other words, the inactive compound is ingested, and once in the body, it is processed into its active compound.
In yet another such study, but with researchers this time looking into the clinical implications and importance of DDIs between anticancer agents and CBD in patients with cancer, the reviewers found that there was limited information available, with most of the data coming from in vitro studies and that the true in vivo implications are not well-known. This lead them to believe that erring on the side of caution is the best option, and that doctors and pharmacists should always consider the possibility of interactions and their consequences whenever they are aware of a patient using CBD products.