Anticoagulation with anisindione in a patient with a warfarin-induced skin eruption

A 71-year-old woman experienced a pruritic, maculopapular, morbilliform rash on her lower extremities 5 days after starting warfarin for recurrent deep vein thrombosis. The rash extended to her truncal areas and progressively worsened until somewhat painful vesicular lesions developed. Warfarin was discontinued, and subcutaneous injections of enoxaparin were begun; the rash resolved. In addition to a history of deep vein thrombosis, the patient had experienced a hypersensitivity skin reaction to warfarin in the past that necessitated withdrawal of the drug and placement of a vena caval filter. Because no clear consensus exists on whether dyes used in compounding warfarin play a causative role or whether allergic cross-sensitivity occurs among the coumarin derivatives, the patient was rechallenged with a dye-free warfarin 10-mg tablet. The pruritic rash returned along with the vesicular lesions and continued to worsen until the warfarin was discontinued again. The patient subsequently was given oral anticoagulant therapy with anisindione, an indanedione, and her symptoms resolved completely. Health care providers managing patients who are receiving oral anticoagulant therapy should be aware of the maculopapular allergic reactions associated with warfarin and consider alternative treatment options such as anisindione.