Warfarin treatment of chronic idiopathic urticaria and angio-oedema

Background Chronic idiopathic urticaria is a disabling condition that does not always respond to antihistamine drugs and other agents are sometimes ne eded to control disease activity. Warfarin has demonstrated efficacy in sin gle unblinded case studies [1] but has been dismissed by others [2]. Objective We investigated the effect of warfarin treatment in eight patient s with chronic idiopathic urticaria unresponsive to antihistamines in an op en study. Six of the eight patients responded to treatment and three had a dramatic response. These three were included in a double-blind placebo-cont rolled trial of warfarin therapy to confirm significant benefit from treatm ent. Methods The three warfarin responders had their stable warfarin dose encaps ulated and placebo capsules were provided. A double-blind placebo-controlle d crossover trial was performed on each patient. Visual analogue scores rec orded disease activity. Results Comparison of visual analogue scores showed a significant benefit w hile on warfarin with a reduction in pruritus and angio-oedema. Conclusion This is the first double-blind placebo-controlled study to show a response of chronic idiopathic urticaria to warfarin. The mechanisms of a ction are unclear and require further study.