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Case report: Medical cannabis-warfarin drug-drug interaction
Tyan F Thomas1, Evdokia S Metaxas2, Thu Nguyen2
1Philadelphia College of Pharmacy, University of the Sciences, Griffith Hall 108 N, 600 S. 43rd Street, Philadelphia, PA, 19104, USA. t.thomas@usciences.edu.
Journal of Cannabis Research
|January 11, 2022
Summary
This study examined an elderly patient using warfarin and medical cannabis (THC/CBD). Unlike other reports, this patient showed minimal INR changes, suggesting cannabis-warfarin interactions may depend on dosage and administration route.
Area of Science:
- Pharmacology
- Drug Interactions
- Cannabinoid Therapeutics
Background:
- Warfarin remains a primary anticoagulant despite newer agents.
- Numerous warfarin drug interactions are known, but interactions with THC and CBD are less understood.
- Existing literature suggests cannabis may potentiate warfarin's effect.
Purpose of the Study:
- To describe a case of concurrent warfarin and medical cannabis (THC/CBD) use.
- To investigate the lack of expected warfarin-cannabis interaction in an elderly patient.
- To explore factors influencing potential warfarin-cannabis interactions.
Main Methods:
- A case report of an 85-year-old patient on warfarin therapy.
- Administration of an oromucosal medical cannabis regimen containing delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).
- Monitoring of International Normalized Ratio (INR) fluctuations over a 12-month period.
Main Results:
- The patient exhibited minimal INR fluctuations despite daily use of medical cannabis (THC and CBD).
- This contrasts with previous case reports suggesting a potential increase in warfarin's effect with cannabis use.
- No significant adverse events related to the combined therapy were observed.
Conclusions:
- Concurrent use of warfarin and medical cannabis (THC/CBD) did not lead to significant INR changes in this elderly patient.
- The route of administration and dosage of cannabis products may influence the interaction with warfarin.
- Further research is needed to elucidate the precise mechanisms and clinical significance of warfarin-cannabis interactions.
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