CBD Drug Interactions

CBD (cannabidiol) is seemingly everywhere, with oils, tinctures, pills, chocolates, gummy bears, and creams available all over the internet, at national drugstore chains, and perhaps at your local farmer’s market — even if you don’t live in a state where medical or recreational marijuana is legal.

CBD, a type of chemical known as a cannabinoid, is a mainingredient in hemp, one type of cannabis plant. Marijuana, another type of cannabis plant, also has some CBD but an abundance of THC (tetrahydrocannabinol), an intoxicating cannabinoid known for making users feel “stoned” or “high.” While CBD won’t get you high, it interacts with cannabinoid receptors in your body and may have effects that are sought by people with arthritis, such as pain relief, reduced inflammation, and improvements in sleep and anxiety.

According to CreakyJoints research presented at the 2019 Annual European Congress of Rheumatology meeting earlier this year, 52 percent of respondents reported having tried CBD for a medical reason. Of those who did, 93 percent said it helped. More than half said they wanted more information on CBD from their doctor, but 58 percent of those who told their doctors about their CBD use did not get the information on safety, effectiveness, and dosing they were looking for.

One common concern among people with chronic illness who use CBD is whether CBD can interfere with prescription drugs you may take for arthritis or other conditions.

We put commonly asked questions to Nina M. Bemben, PharmD, BCPS, a specialist in drug interactions who is trying to educate other pharmacists about possible drug-drug interactions with CBD, as well as Rachna Patel, DO, a physician who does consultations about medical marijuana and CBD and sells her own line of CBD products.

What kind of drug interactions can happen with CBD?

A huge number of medications, including CBD, are broken down by the same large family of liver enzymes, called CYP450.

CBD inhibits some enzymes in this family. This makes them break down certain drugs more slowly, which could potentially increase side effects unless your doctor adjusts the dose. On the other hand, CBD induces other enzymes in this family, which speeds the breakdown of certain drugs so they may potentially be less effective unless the dose is increased.

As examples, you may experience increased side effects if CBD is used along with these drugs:

  • Antidepressants (such as fluoxetine, or Prozac)
  • Medications that can cause drowsiness (antipsychotics, benzodiazepines)
  • Macrolide antibiotics (erythromycin, clarithromycin)
  • Heart medications (some calcium channel blockers)

“There is still a lot of uncertainty about how CBD interacts with drug-metabolizing enzymes in the body. We know that there are some drug-metabolizing enzymes that are affected by CBD, some that are not, and many others where we just don’t have any information yet,” says Dr. Bemben.

What do we know for sure about CBD’s interactions with other drugs?

The most direct information comes from studies on the only FDA-approved CBD product, Epidiolex, which is used to treat rare forms of epilepsy. Epidiolex has been found to increase blood levels of the blood thinner warfarin about 30 percent, which raises the risk of bleeding. It also interacts with other medications used for epilepsy.

“The manufacturer of Epidiolex was asked by the FDA to conduct more drug-drug interaction studies, so we will learn more about CBD’s interactions with other drugs in the future,” says Dr. Bemben.

Can CBD interact with medications I take specifically for arthritis?

“Based on what we know now about the way CBD is metabolized, I would not expect significant drug-drug interactions with drugs commonly used in arthritis treatment, such as methotrexate, and most nonsteroidal anti-inflammatory drugs (NSAIDs). I would advise caution on one NSAID, diclofenac, because there isn’t information on how CBD affects — if at all — the enzyme that metabolizes it,” says Dr. Bemben.

Rheumatologists are always on the alert for liver problems that may result from arthritis medications, and that includes CBD as well as NSAIDs and methotrexate.

Are older people more at risk of CBD drug interactions?

Yes, for several reasons. “As we age, our livers and kidneys may be slower to eliminate drugs from the body. In addition, older patients and those with chronic health problems are more likely to be using multiple medications, so the risk for drug interactions increases,” says Dr. Bemben.

Dr. Patel worries in particular about any side effects or interactions that result in dizziness and may increase the risk of falls in the elderly. For example, using the antidepressant fluoxetine together with cannabis products can increase dizziness and drowsiness.

Are there some people who should stay away from CBD?

Hold off if you have known liver damage, says Dr. Patel. In a study done on mice published earlier this year, the dose of CBD used to protect against seizures was found to induce liver damage. According to other animal research, CBD may increase levels of liver enzymes, raising concerns about liver toxicity in patients taking methotrexate.

“We use other therapies that cause liver injury, like nonsteroidal anti-inflammatories (NSAIDs). If liver enzymes go up in someone on methotrexate, we would generally hold the drug other than methotrexate [for example, CBD or an NSAID] to see if the enzyme levels normalize,” says Michael Weinblatt, MD, professor of medicine at Harvard Medical School in Boston.

People who take Epidiolex for epilepsy are more likely to develop abnormal liver enzymes, as well as sleepiness and other symptoms, if they are also using valproic acid to control seizures.

“This is important for people with arthritis to know because valproic acid is sometimes used for pain that isn’t controlled by other medications,” says Dr. Patel.

If I stick with a CBD cream, does that reduce the risk of drug interactions?

Probably, since little if any of a topical product is likely to be absorbed into your system. “Unfortunately, we just don’t have good information about how much of a topical CBD product gets absorbed. This can be influenced by the inactive ingredients in the product, where on the body it’s applied, and whether you apply a bandage over the area after applying it,” says Dr. Bemben.

While topical CBD products may not be absorbed deeply enough to raise concerns about drug interactions, that also means they may not be as effective for arthritis pain. “If you just have one joint hurting and it’s close to the surface, using a topical would be appropriate. It’s not as likely to help a hip or other deep joint,” says Dr. Patel.

Which health professionals need to know I’m trying CBD?

Tell your rheumatologist and anyone else who prescribes medication for you. If you need surgery, an anesthesiologist may choose a different dose or type of anesthesia if you’re using CBD.

“If you fill all of your medications at the same pharmacy, your pharmacist will be able to assess for drug interactions for all of them, regardless of who prescribed them. You should still let the pharmacist know about over-the-counter medications, herbs, and supplements — including CBD — that you don’t get through the pharmacy. It is important to bring the CBD product to your doctor and pharmacist so they can check the amount of CBD and other ingredients it contains,” says Dr. Bemben.

“While patients may be wary of stigma surrounding CBD products, I believe most health care providers understand this is a growing area and one strategy patients are trying in hopes of getting relief,” she says.

Is there an online source I can use to figure out which of my medications might interact with CBD?

Online databases are available to help health professionals evaluate potential drug-drug interactions, at a price. “Freely available resources tend to be less reliable, and this highlights the importance of discussing all your medications, including CBD, with your doctor and pharmacist,” says Dr. Bemben.

One source available to patients is drugs.com, where you can plug in either cannabidiol (which will give you the FDA-approved oral product Epidiolex) or cannabis (which will give you both THC and CBD) and check for possible interactions with other medications you take.

Has anyone had a life-threatening drug interaction with CBD?

“There haven’t been reports of serious drug-drug interactions with over-the-counter CBD products. However, these products are relatively new and it typically takes time for reports to be published. We have very little information about over-the-counter CBD products and how they may interact with other drugs,” says Dr. Bemben.

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