ALLERGIC REACTIONS TO STREPTOKINASE - DOES ANTIBODY-FORMATION PREVENT REUSE IN A 2ND MYOCARDIAL-INFARCTION

Thrombolytic therapy is established as effective treatment of acute myocardial infarction. About 20% of patients eligible for thrombolytic therapy have suffered a previous infarction, and about 9% of patients who receive thrombolytic therapy will suffer another infarction within a year. It is therefore important to know whether readministration of thrombolytic agents is as safe and effective as initial administration. Streptokinase is a widely used thrombolytic agent. Because it is a foreign bacterial protein, it is antigenic. Antibodies to streptokinase develop within 3 to 4 days of administration, reaching a peak about 2 weeks later. Antibody levels then fall slowly, but a number of studies have shown that antistreptokinase antibody titres remain increased for several years after therapy. If streptokinase is readministered to patients with high antibody levels, there may be a higher incidence of allergic reactions, and efficacy may be compromised. Tests in vitro of streptokinase-neutralising capacity suggest that up to 51% of patients may have sufficient levels of antibody to neutralise a standard dose of streptokinase as long as 4 years after initial streptokinase therapy. It is therefore recommended that patients who have received streptokinase should not receive it again. Alternative agents such as alteplase or urokinase should be given if repeat thrombolytic therapy is required.