Anesthetic complications of a weight reducing regimen.

A previous report of two similar cases of urticaria controlled by warfarin did not include a placebo challenge.' Our case differed from those cases in that we had to keep the prothrombin time within the therapeutic range. The mechanism of this response to warfarin is obscure, but there may be a link between urticaria and the coagulation system.2-5 Ryan proposed that plasmin may contribute to urticaria through activating the complement cascade, activating kallikrein, and producing degradation products of fibrin which also promote inflammation.2 There are also several reports of chronic urticaria and angio-oedema responding to the plasmin inhibitors tranexamic acid34 and aprotinin.' Warfarin could affect plasmin activity in two ways: firstly, by reducing the formation of fibrin and, secondly, by reducing protein C concentrations. Reduced formation of fibrin may also be important in itself as fibrin may perpetuate inflammation in chronic urticaria.2 We suggest that further investigation of the role of the coagulation system and the use of warfarin in chronic urticaria would be of value.