Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
J Pharm Pract. 2020 Dec;33(6):915-918. doi: 10.1177/0897190019854958. Epub 2019 Jul 18.
To report a probable interaction between warfarin and edible cannabis that resulted in an elevated international normalized ratio (INR) without bleeding complications. A 35-year-old Middle Eastern male on warfarin long term with an INR goal of 2.5 (accepted range: 2.0-3.0). The patient has generally been stable on warfarin 10 mg daily from 2010 to 2018, until INR suddenly increased to 7.2 following 1 month of edible cannabis ingestion and cannabis smoking. Patient denied any signs and symptoms of bleeding. No other reasonable causes of the elevation in INR were apparent. The patient was advised to hold 2 doses of warfarin and discontinue cannabis use. The INR dropped below 4 upon discontinuation of cannabis with dose adjustments to warfarin.
The elevation in INR can be explained by the inhibition of CYP2C9 by cannabis use causing decreased metabolism of warfarin. The interaction between warfarin and cannabis was determined to be probable using the Horn Drug Interaction Probability Scale.
There are no previous reports of interactions between edible cannabis and warfarin, with very few case reports describing the interaction with other forms of cannabis. Close monitoring of INR in patients with concomitant cannabis is recommended for proper warfarin management.
报告一例华法林与食用大麻可能发生的相互作用，导致 INR 升高而无出血并发症。 一名中东裔 35 岁男性，长期服用华法林，INR 目标值为 2.5（接受范围：2.0-3.0）。该患者自 2010 年至 2018 年一直稳定服用华法林 10mg/天，直到 1 个月前食用大麻并吸食大麻后 INR 突然升高至 7.2。患者否认有任何出血迹象或症状。INR 升高没有其他明显的合理原因。建议患者停用华法林 2 剂，并停止使用大麻。停止使用大麻并调整华法林剂量后，INR 降至 4 以下。
大麻使用抑制 CYP2C9 ，导致华法林代谢减少，从而导致 INR 升高。使用 Horn 药物相互作用概率量表确定华法林与大麻之间的相互作用为可能。
目前尚无食用大麻与华法林相互作用的报道，仅有少数病例报告描述了与其他形式大麻的相互作用。建议同时使用大麻的患者密切监测 INR，以进行适当的华法林管理。
