My 13 reasons for marijuana use post-stroke.
Don't follow me, I'm not medically trained.
Interaction between warfarin and cannabis
First published: 16 October 2018
This article has been accepted for publication and undergone
full peer review but has not been through the copyediting, typesetting,
pagination and proofreading process, which may lead to differences
between this version and the Version of Record. Please cite this article
as doi: 10.1111/bcpt.13152
Abstract
Delta‐9‐tetrahydrocannabinol (THC), the main psychoactive
cannabinoid in cannabis, may inhibit the cytochrome P450 enzyme CYP2C9.
Consequently, cannabis use might infer a risk of drug‐drug interaction
with substrates for this enzyme, which includes drugs known to have a
narrow therapeutic window. In this study, we describe a case report of a
27‐year‐old man treated with warfarin due to mechanical heart valve
replacement who presented with elevated international normalized ratio
(INR) value (INR = 4.6) following recreational cannabis use. We
conducted a review of the available literature, using the PubMed and
EMBASE databases while following PRISMA guidelines. Following screening
of 85 articles, three eligible articles were identified, including one in vitro study and two case reports. The in vitro
study indicated that THC inhibits the CYP2C9‐mediated metabolism of
warfarin. One case study reported of a man who on two occasions of
increased marijuana use experienced INR values above 10 as well as
bleeding. The other case study reported of a patient who initiated
treatment with a liquid formulation of cannabidiol (CBD) for the
management of epilepsy, ultimately necessitating a 30% reduction in
warfarin dose to maintain therapeutic INR values. The available,
although sparse, data suggest that use of cannabinoids increase INR
values in patients receiving warfarin. Until further data are available,
we suggest patients receiving warfarin be warned against cannabis
smoking.
This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
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