Which scenario is a contraindication to IV streptokinase in myocardial infarction?

• A. MI within past 12 hours
• B. Multiple-site MI
• C. Treatment with streptokinase within the past 30 days
• D. Uncomplicated inferior or posterior MI

Answer: (C)

Streptokinase can trigger a strong immune response if a patient has been exposed to it before, so recent exposure creates antibodies that can cause a hypersensitivity reaction and also neutralize the drug’s effect. Because of this, administering streptokinase again within a short timeframe—about the past month—is a contraindication to its use in acute myocardial infarction. The drug’s mechanism relies on forming a plasminogen-streptokinase complex to promote clot breakdown, but preformed antibodies from prior exposure can both provoke anaphylaxis and reduce efficacy, making re-treatment unsafe. The other scenarios do not involve recent exposure to streptokinase, so they don’t carry this specific contraindication.