Pitcock James J, Oluyemi Olubusola O, Pitcock Margaret B
The University of Mississippi School of Pharmacy, The University of Mississippi Hospitals and Clinics, Jackson, Mississippi.
Pharmacotherapy. 2013 Nov;33(11):e333-6. doi: 10.1002/phar.1284. Epub 2013 May 3.
Warfarin, an anticoagulant with a narrow therapeutic window, is largely metabolized by cytochrome P450 2C9. Isopropyl alcohol has been shown to inhibit the activity of this enzyme. Use of topical isopropyl alcohol as a rubefacient may place patients at risk for systemic exposure. Isopropyl alcohol's effect on the international normalized ratio (INR) has not been well characterized. We describe five patients who experienced INR elevations after topical application of isopropyl alcohol. Each patient's INR was therapeutic for at least seven visits prior to becoming supratherapeutic. All patients confirmed drug adherence and denied medication or dietary changes. Seventy percent isopropyl alcohol was used in all cases over a large body surface area of intact skin multiple times daily for several days. All patients experienced a 10% or greater increase in their INR compared to previous levels. On discontinuation of isopropyl alcohol, each patient's INR returned to and remained in therapeutic range for the next 2 months. Prediction of isopropyl alcohol's effect of the INR is confound by several factors, notably the BSA covered, concentration of alcohol in the product, contact time with the skin, and skin integrity. It is important that clinicians inquire about the use of isopropyl alcohol and educate patients about its potential risk in those receiving warfarin therapy.
华法林是一种治疗窗狭窄的抗凝剂，主要由细胞色素P450 2C9代谢。异丙醇已被证明会抑制该酶的活性。局部使用异丙醇作为发红剂可能会使患者面临全身暴露的风险。异丙醇对国际标准化比值（INR）的影响尚未得到充分表征。我们描述了5例局部应用异丙醇后INR升高的患者。在每个患者的INR超过治疗范围之前，其INR在至少7次就诊时均处于治疗水平。所有患者均确认坚持服药，并否认有药物或饮食变化。所有病例均使用70%的异丙醇，每天多次涂抹于大面积完整皮肤，持续数天。与之前的水平相比，所有患者的INR均升高了10%或更多。停用异丙醇后，每个患者的INR在接下来的2个月内恢复并保持在治疗范围内。异丙醇对INR的影响预测受到几个因素的混淆，特别是覆盖的体表面积、产品中的酒精浓度、与皮肤的接触时间以及皮肤完整性。临床医生询问患者是否使用异丙醇并对接受华法林治疗的患者进行其潜在风险的教育很重要。
