Warfarin-Induced Pseudo-Allergy

Abstract

Most common adverse reactions to warfarin are fatal and nonfatal hemorrhage from any tissue or organ. Despite bleeding complications being the most feared concern, non-bleeding events can also occur from warfarin therapy. These non-bleeding events, which account for less than 1%, include but are not limited to skin necrosis and dermatological hypersensitivity reactions. We describe a rare case of “warfarin allergy” in a 77-year-old female patient admitted for coronary bypass grafting and mitral/aortic valve replacement. The patient came with a history of valvular heart disease, embolism (occlusion of distal superficial femoral artery) and atrial fibrillation with documented warfarin allergy described as dermatitis and anaphylaxis witnessed during earlier hospital admission. Given double valve replacement and atrial fibrillation (CHA₂DS₂-VASc score of 9), she was deemed a candidate for lifelong warfarin. Significant renal impairment and recent valve replacement narrowed the choice of anticoagulant to warfarin. To rule out the possibility of dye allergy, patient was re-challenged with dye free warfarin with close monitoring. Patient was able to tolerate dye free (white) warfarin with no allergic manifestation. The purpose of this report is to increase awareness of possibility of allergic reaction to dye in medications and recommend possibility of dye free medications as an option in such cases.




J Hematol. 2014;3(4):116-117
doi: http://dx.doi.org/10.14740/jh173w