Department of Pharmacy, Clinical and Administrative Sciences, College of Pharmacy, The University of Oklahoma, Oklahoma City, OK 73126, USA.
Clin Appl Thromb Hemost. 2012 Jan-Feb;18(1):107-9. doi: 10.1177/1076029611418963. Epub 2011 Sep 2.
We describe a case of a 41-year-old woman who was stable for over a year on 22.5 mg/week of warfarin. At a follow-up visit, her international normalized ratio (INR) was found to be supratherapeutic at 3.9. Her only significant change was acyclovir initiation for shingles, and clindamycin and dapsone for infection on her right foot. An interaction report was run using Micromedex with no interactions reported. Sixteen percent of the weekly dose was held and maintenance dose was continued. Two weeks later, the INR remained supratherapeutic at 4.3, with discontinuation of clindamycin and dapsone, 5 days earlier, as the only change. This time an interaction report was run using Lexi-Comp, which identified an interaction between warfarin and dapsone. The INR has been therapeutic and stable since discontinuation of transient factors. It is hypothesized that warfarin and dapsone compete for binding on the CYP2C9 and CYP3A4 isoenzymes and therefore serum concentration of warfarin was elevated.
我们描述了一例 41 岁女性的病例，她在每周 22.5 毫克华法林的治疗下稳定了一年多。在一次随访中，发现她的国际标准化比值（INR）高于治疗范围，为 3.9。她唯一的重大变化是因带状疱疹开始使用阿昔洛韦，以及右脚感染开始使用克林霉素和氨苯砜。使用 Micromedex 运行了药物相互作用报告，但没有报告相互作用。每周剂量的 16%被暂停，维持剂量继续。两周后，INR 仍高于治疗范围，为 4.3，克林霉素和氨苯砜在 5 天前停药，这是唯一的变化。这一次，使用 Lexi-Comp 运行了药物相互作用报告，发现华法林和氨苯砜之间存在相互作用。自暂时因素停止后，INR 一直处于治疗范围内且稳定。据推测，华法林和氨苯砜竞争结合 CYP2C9 和 CYP3A4 同工酶，因此华法林的血清浓度升高。
