A form of drug-induced angioedema/anaphylactoid reaction that is occasionally produced by fibrinolytic agents such as tPA may be dependent on contact system components, as shown by the inhibition of tPA-induced iBK formation by M202-H03, DX-4012, corn trypsin inhibitor and C1-INH (Figures 11, 12). This evidence concerns the gene SERPING1 and angioedema.