How safe is the readministration of streptokinase?

Streptokinase is an antigenic thrombolytic agent used for the treatment of acute myocardial infarction. It reduces mortality as effectively as the nonantigenic alteplase in most infarct patients while having the advantage of being much less expensive. This cost implication is important since myocardial reinfarction is common, with fibrinolytic therapy indicated in many patients with reinfarction. Following streptokinase, antistreptokinase antibodies and neutralisation titres can rise to significant levels from 4 days after the initial dose. These antibodies can presist for at least 4 years in up to 50% of patients. It is possible that these antibodies may cause allergic reactions or neutralisation of a further dose of streptokinase, rendering it ineffective for the treatment of myocardial reinfarction. To date, 2 small studies of patients without previous streptokinase exposure suggest that higher antibody titres are associated with a lower rate of coronary reperfusion, while a further study suggests that high titres are associated with hypersensitivity reactions. At present the readministration of streptokinase cannot be recommended from 4 days after a first dose. Further larger studies are needed to assess the effect of high neutralisation titres on coronary reperfusion.