Revisiting CBD Drug Interactions

Share This Post

Share on facebook
Share on linkedin
Share on twitter
Share on email

The May issue of The Rx Consultant focused on cannabidiol (CBD) and included a brief summary of drug interactions. We’d like to provide some additional information on potential interactions with CBD.

CBD inhibits the drug-metabolizing enzyme CYP2C19, and may increase serum levels of CYP2C19 substrates like proton pump inhibitors, diazepam, clobazam, and certain antidepressants. Some in vitro and animal studies have suggested that CBD is also an inhibitor of CYP2C9 (which metabolizes warfarin), albeit to a lesser extent. A larger dose of CBD may be required to inhibit CYP2C9 compared with CYP2C19. While there are no human studies confirming an interaction with 2C9 substrates, a 2018 case report describes a patient who was taking warfarin after a mitral valve replacement and started on CBD for the management of treatment-resistant epilepsy. Over about 17 months, his CBD dose was increased from 5 to 35 mg/kg per day and his INR increased with the dose. After about 12 months, his warfarin dose had been lowered from 7.5 mg/day to an average of 5.36 mg/day. There were no bleeding complications.

Because CBD may increase serum levels (and possibly side effects) of CYP2C9 substrates (including the NSAIDs diclofenac, ibuprofen, meloxicam and celecoxib; amitriptyline; warfarin; glipizide; and losartan), cautioned is advised with combined use of CBD and CYP2C9 substrates. Individuals with a genetic variant of the 2C19 or 2C9 enzyme are poor metabolizers of the respective substrates and may be more susceptible to CBD-drug interactions. In patients taking warfarin, INR monitoring has been suggested during initiation of CBD and when CBD doses are increased.

Grayson L, et al. Epilepsy Behav Case Rep. 2018; 9: 10–11.

More To Explore

What is The Rx Consultant?

The Rx Consultant is a subscription-based service that delivers practical updates & reviews covering all the top-selling drugs and common health conditions. All our publications focus on the facts busy front-line pharmacists and other health care practitioners need to stay current, and provide it a streamlined, easy reading style.

For 30 years The Rx Consultant has operated independent of the pharmaceutical industry and has no commercial bias.

Join thousands of healthcare providers who enjoy the following benefits every month.

1. Drug Therapy Updates & Reviews

The eLibrary contains over 30 streamlined updates on drug therapy for the most common diseases. New articles are added every month – it is a continually expanding resource.

2. Continuing Education

The eLibrary includes 50+ hours of Pharmacology CE from an ACPE approved provider at no additional charge. Each article provides at least 1.5 hours of Pharmacology CE. Subscribers can take their tests online, score them immediately, then print or save their credit statements. Pharmacology CE tests can also be mailed, faxed, or even phoned in to The Rx Consultant office, and credit statements will be delivered by mail or fax.

3. Unlimited Access to our Resource Library, with:

  • Healthcare News

    The eLibrary includes a news column covering the developments that matter most to nurse practitioners and other front-line providers. You get a headline, the bottom line, and how it’s likely to affect your practice in a few short lines, then it’s on to the next news item. The news briefs are also available in print monthly as Rx News Connection.
  • Patient Education Pages

    Patient Q&A to sharpen your skills in educating patients and answering common questions.
  • Charts & Tables

    At-a-glance updates on drugs, doses, common side effects & interactions
  • Quick Facts

    Key facts organized for fast access both online and on handy reference cards.
  • The Bottom Line

    Our members suggest the topics and each issue undergoes a rigorous three month peer reviewed process. Our CE is different because we accept no grants, advertising, or funding of any kind from drug manufacturers. With no financial ties, maintaining a bias-free publication is a straightforward process.

The Rx Consultant maintains a high standard for quality

And a rigorous system for content development that insures it. Every issue is written by an expert in the topic area, and then peer reviewed, fact-checked and edited to insure that the content is

  • Evidence-based
  • Non-Biased
  • Balanced
  • Timely
  • Accurate and
  • Useful for community practitioners

The Rx Consultant is completely independent of the pharmaceutical industry.

We accept no grants, advertising, or funding of any kind from drug manufacturers. With no financial ties, maintaining a bias-free publication is a straightforward process.