What is the best choice between urokinase and streptokinase (thrombolytic agents) in the management of acute myocardial infarction (MI)?

Comparison of Urokinase vs Streptokinase in Acute Myocardial Infarction

Fibrin-specific agents such as tissue plasminogen activator (t-PA) are preferred over both urokinase and streptokinase for the management of acute myocardial infarction due to their superior efficacy and safety profiles. 1

Efficacy Comparison

When directly comparing urokinase and streptokinase:

• Patency rates: Urokinase shows higher early patency rates (71.8% vs 48.0% at 60 minutes) compared to streptokinase, though this difference narrows by 90 minutes (71.2% vs 63.9%) 2

• Thrombolytic efficacy: When used intracoronary, both agents demonstrate similar efficacy in opening occluded arteries (60% for urokinase vs 57% for streptokinase) 3

• Mortality benefit: Both agents provide mortality reduction, with streptokinase showing approximately 22% reduction in the odds of death in early trials 4

Safety Profile Comparison

• Systemic fibrinolysis: Urokinase causes less systemic fibrinolysis than streptokinase, with significantly fewer patients experiencing severe fibrinogen depletion 3

• Bleeding complications: Urokinase is associated with fewer bleeding complications compared to streptokinase (11% vs 29%) 3, 2

• Hypotension: Streptokinase administration may be associated with hypotension, though severe allergic reactions are rare 1

• Reuse limitations: Streptokinase should not be re-administered since antibodies persist for at least 10 years, which can impair its activity and increase risk of allergic reactions 1

Current Guidelines Recommendation

Current guidelines from the European Society of Cardiology (2018) recommend:

1. Fibrin-specific agents should be preferred over non-fibrin specific agents like streptokinase 1

2. Single-bolus weight-adjusted tenecteplase (TNK-tPA) is equivalent to accelerated t-PA in reducing 30-day mortality but is safer in preventing non-cerebral bleeds and easier to use in pre-hospital settings 1

3. Neither urokinase nor streptokinase is currently recommended as first-line therapy for acute MI when fibrin-specific agents are available 1

Important Considerations

• Time to treatment: Early administration of thrombolytic therapy is crucial, with greater mortality reduction when treatment is given within the first 2 hours (44% vs 20% for those treated later) 1

• Adjunctive therapy: All thrombolytic regimens should include:

  • Aspirin (150-325 mg initial dose, chewed)
  • Clopidogrel (added to aspirin for patients receiving fibrinolysis)
  • Appropriate anticoagulation 1

• Contraindications: Both agents share similar contraindications including recent hemorrhagic stroke, known intracranial neoplasm, active internal bleeding, and suspected aortic dissection 1

Practical Algorithm for Thrombolytic Selection

1. First choice: Fibrin-specific agents (t-PA, TNK-tPA) when available

   • Better mortality outcomes with accelerated t-PA (10 fewer deaths per 1000 patients compared to streptokinase) 1
   • Single-bolus TNK-tPA offers equivalent mortality benefit with fewer non-cerebral bleeds 1

2. If fibrin-specific agents unavailable:

   • Urokinase may be preferred over streptokinase when:
     • Early coronary bypass surgery is anticipated (less perioperative bleeding) 3
     • Patient has previously received streptokinase (antibody formation) 1
     • Higher risk of bleeding complications exists

3. Streptokinase may be considered when:

   • Cost is a significant factor 5
   • No previous exposure to streptokinase
   • Lower risk of stroke is prioritized (t-PA has slightly higher stroke risk) 1

Common Pitfalls and Caveats

• Do not re-administer streptokinase due to antibody formation and risk of allergic reactions 1
• Monitor for hypotension with streptokinase; temporarily halt infusion if it occurs 1
• Both agents are now largely superseded by fibrin-specific agents in modern practice 1
• The optimal time window for thrombolytic therapy is within 12 hours of symptom onset, with greatest benefit in the first 2 hours 1