Does Cannabidiol (CBD) Interact With Prescription Medication?

In our latest question and answer, the pharmacist discusses whether or not Cannabidiol (CBD) interacts with prescription medication.

Question

My doctor recommended that I try CBD oil (hemp with less than 1mg THC per serving) for pain and anxiety due to a chronic Lyme. Can I safely take CBD with the other medications that I'm on. These would include 20mg Protonix, 5-7mg Elavil (I break the 10mg pill in half), 0.25-0.5mg Lorazepam, 150mg Zantac. I take all of these once daily. I also take 400mg magnesium glycinate, 5000iu vitamin D, and 50mg of 5-htp, also once daily. 

Asked by Anon On Feb 22, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Feb 22, 2018

Cannabidiol, also known as CBD, is a major constituent of cannabis (i.e. marijuana) and is considered non-psychoactive. In fact, while THC is the more well known component of cannabis, cannabidiol makes up nearly 40% of cannabis extracts. 


Does CBD Have Drug Interactions?

There is a decided lack of information regarding drug interactions between prescription medication and cannabidiol (CDB). It is therefore very difficult to give appropriate guidance to individuals when it comes to their specific medication list and whether or not anything interacts with CBD.


In the studies that have been conducted, CBD appears to have significantly few drug interactions. This may be due to the lack of studies on the matter or it may be because CBD simply does not have many interactions.


CBD has however, been studied fairly extensively in regard to its anti-epileptic (i.e. anti-seizure) effect and appears to be extremely effective and safe when compared to traditional pharmaceuticals. More well controlled studies are needed however.


As CBD has been mainly studied for seizure control, there is some information available regarding drug interactions with prescription anti-epileptic drugs. One recent study found that CBD may interact with some of the more commonly used anti-epileptic drugs including:

  • Topamax (topiramate): Concentrations of Topamax may increase when used in conjunction with CBD products.
  • Zonegran (zonisamide): Concentrations of Zonegran may increase when used in conjunction with CBD products.
  • Onfi (clobazam): Concentrations of Zonegran may decrease when used in conjunction with CBD products.


The mechanism of the drug interactions may be due to how CBD affects certain CYP metabolizing enzymes in the body. Studies have shown that CBD can inhibit CYP 2C19 and CYP 3A, two major metabolizing enzymes in the body. Alterations to these metabolizing enzymes can theoretically affect blood concentrations of many different medications.


Interestingly enough however, is that although there is pretty definitive proof that CBD does affect CYP metabolizing enzymes, it doesn't always lead to clinically significant changes in drug concentrations. In fact, it is unknown whether or not the inhibition of these metabolizing enzymes only occur in a lab setting (i.e. in vitro) as most studies show minimal to no changes in humans.


CBD is considered by most to be a safe medication, with extremely high doses proving to be well tolerated and effective for certain individuals. Doses up 1,500 mg per day have been used safely, which is somewhat astonishing considering doses as low as 1 mg can be effective for a variety of indications. Unfortunately, there are just so few studies in regard to drug interactions to give definitive statements regarding whether or not CBD interacts with a given medication.


It is recommended that you speak with your doctor regarding CBD use and how it may affect your medications. You and your doctor may decide to try and use it while being monitored for any adverse effects or drug interactions.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of PharmacistAnswers.com. He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Brian.Staiger@PharmacistAnswers.com Office: 716-389-3076

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