CBD and other medications: Proceed with caution
Products containing cannabidiol (CBD) seem to be all the rage these days, promising relief from a wide range of maladies, from insomnia and hot flashes to chronic pain and seizures. Some of these claims have merit to them, while some of them are just hype. But it won’t hurt to try, right? Well, not so fast. CBD is a biologically active compound, and as such, it may also have unintended consequences. These include known side effects of CBD, but also unintended interactions with supplements, herbal products, and over-the-counter (OTC) and prescription medications.
Doubling up on side effects
While generally considered safe, CBD may cause drowsiness, lightheadedness, nausea, diarrhea, dry mouth, and, in rare instances, damage to the liver. Taking CBD with other medications that have similar side effects may increase the risk of unwanted symptoms or toxicity. In other words, taking CBD at the same time with OTC or prescription medications and substances that cause sleepiness, such as opioids, benzodiazepines (such as Xanax or Ativan), antipsychotics, antidepressants, antihistamines (such as Benadryl), or alcohol may lead to increased sleepiness, fatigue, and possibly accidental falls and accidents when driving. Increased sedation and tiredness may also happen when using certain herbal supplements, such as kava, melatonin, and St. John’s wort. Taking CBD with stimulants (such as Adderall) may lead to decreased appetite, while taking it with the diabetes drug metformin or certain heartburn drugs (such as Prilosec) may increase the risk of diarrhea.
CBD can alter the effects of other drugs
Many drugs are broken down by enzymes in the liver, and CBD may compete for or interfere with these enzymes, leading to too much or not enough of the drug in the body, called altered concentration. The altered concentration, in turn, may lead to the medication not working, or an increased risk of side effects. Such drug interactions are usually hard to predict but can cause unpleasant and sometimes serious problems.
Researchers from Penn State College of Medicine evaluated existing information on five prescription CBD and delta-9-tetrahydrocannabinol (THC) cannabinoid medications: antinausea medications used during cancer treatment (Marinol, Syndros, Cesamet); a medication used primarily for muscle spasms in multiple sclerosis (Sativex, which is not currently available in the US, but available in other countries); and an antiseizure medication (Epidiolex). Overall, the researchers identified 139 medications that may be affected by cannabinoids. This list was further narrowed to 57 medications, for which altered concentration can be dangerous. The list contains a variety of drugs from heart medications to antibiotics, although not all the drugs on the list may be affected by CBD-only products (some are only affected by THC). Potentially serious drug interactions with CBD included
- a common blood thinner, warfarin
- a heart rhythm medication, amiodarone
- a thyroid medication, levothyroxine
- several medications for seizure, including clobazam, lamotrigine, and valproate.
The researchers further warned that while the list may be used as a starting point to identify potential drug interactions with marijuana or CBD oil, plant-derived cannabinoid products may deliver highly variable cannabinoid concentrations (unlike the FDA-regulated prescription cannabinoid medications previously mentioned), and may contain many other compounds that can increase the risk of unintended drug interactions.
Does the form of CBD matter?
Absolutely. Inhaled CBD gets into the blood the fastest, reaching high concentration within 30 minutes and increasing the risk of acute side effects. Edibles require longer time to absorb and are less likely to produce a high concentration peak, although they may eventually reach high enough levels to cause an issue or interact with other medications. Topical formulations, such as creams and lotions, may not absorb and get into the blood in sufficient amount to interact with other medications, although there is very little information on how much of CBD gets into the blood eventually. All of this is further complicated by the fact that none of these products are regulated or checked for purity, concentration, or safety.
The bottom line: Talk to your doctor or pharmacist if using or considering CBD
CBD has the potential to interact with many other products, including over-the-counter medications, herbal products, and prescription medications. Some medications should never be taken with CBD; the use of other medications may need to be modified or reduced to prevent serious issues. The consequences of drug interactions also depend on many other factors, including the dose of CBD, the dose of another medication, and a person’s underlying health condition. Older adults are more susceptible to drug interactions because they often take multiple medications, and because of age-related physiological changes that affect how our bodies process medications.
People considering or taking CBD products should always mention their use to their doctor, particularly if they are taking other medications or have underlying medical conditions, such as liver disease, kidney disease, epilepsy, heart issues, a weakened immune system, or are on medications that can weaken the immune system (such as cancer medications). A pharmacist is a great resource to help you learn about a potential interaction with a supplement, an herbal product (many of which have their own drug interactions), or an over-the-counter or prescription medication. Don’t assume that just because something is natural, it is safe and trying it won’t hurt. It very well might.
CBD drug interactions: Is CBD safe to take with prescription medications?
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.”