Repeat thrombolysis.

Since 20% of patients with myocardial infarction (MI) have had a previous infarction, and reinfarction within one year after infarction occurs in 9% of cases, it is important to clarify the role of repeat thrombolysis. After streptokinase (SK) administration, IgG antibodies rise to a peak at two weeks and slowly fall over the next 12 months, but 50% of patients still have antibody levels sufficient to neutralise a standard dose of SK up to four years after initial SK administration. On this evidence, SK or anistreplase should not be readministered, except perhaps in the first two to three days after initial treatment. The efficacy of tissue plasminogen activator (t-PA) and urokinase is not affected by prior treatment with SK.