Warfarin/Dronabinol; Marijuana Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Dronabinol and marijuana may slow down how quickly your body processes warfarin.

What might happen:

You may experience an increased chance for bleeding including bleeding from your gums, nosebleeds, unusual bruising, or dark stools.

What you should do about this interaction:

Make sure your healthcare professionals (e.g. doctor or pharmacist) know that you are taking dronabinol or using marijuana. You may need to have your bleeding tests (e.g. INR) checked more often, especially when you first start taking dronabinol, if the dose of your dronabinol changes, or if you increase or decrease marijuana use. If you have any signs of bleeding, such as bleeding from your gums, nosebleeds, unusual bruising, or dark stools, contact your doctor right away.Tell your doctor right away if you experience muscle pain, tenderness, or weakness; unexplained tiredness; or discolored urine.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Yamaori S, Koeda K, Kushihara M, Hada Y, Yamamoto I, Watanabe K. Comparison in the in vitro inhibitory effects of major phytocannabinoids and polycyclic aromatic hydrocarbons contained in marijuana smoke on cytochrome P450 2C9 activity. Drug Metab Pharmacokinet 2012; 27(3):294-300.
  • 2.Syndros (dronabinol) US prescribing information. Insys Therapeutics, Inc. May 25, 2017.
  • 3.Yamreudeewong W, Wong HK, Brausch LM, Pulley KR. Probable interaction between warfarin and marijuana smoking. Ann Pharmacother 2009 Jul; 43(7):1347-53.
  • 4.Damkier P, Lassen D, Christensen MMH, Madsen KG, Hellfritzsch M, Pottegard A. Interaction between warfarin and cannabis. Basic Clin Pharmacol Toxicol 2018 Oct 16.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.