In a patient with acute ST‑segment–elevation myocardial infarction, which thrombolytic agent—tenecteplase (Metalyse) or streptokinase—has a lower risk of major and intracranial bleeding?

Tenecteplase (Metalyse) Has Lower Bleeding Risk Than Streptokinase in STEMI Thrombolysis

Tenecteplase is the preferred fibrinolytic agent over streptokinase for STEMI, with demonstrated reduced noncerebral bleeding and no increase in intracranial hemorrhage risk. The 2025 ACC/AHA guidelines explicitly state that fibrin-specific agents like tenecteplase are preferred over non-fibrin-specific agents (streptokinase) due to superior patency rates and less immunogenicity 1.

Evidence Hierarchy Supporting Tenecteplase

The most definitive evidence comes from a large randomized trial (GUSTO-III, n=41,021) comparing fibrinolytic agents in AMI. Tenecteplase demonstrated equivalent 30-day mortality to alteplase but with significantly reduced noncerebral bleeding 1. When compared to streptokinase in this same trial framework, accelerated alteplase (tenecteplase's comparator) showed:

• Intracerebral hemorrhage: 0.7% vs 0.5-0.6% for streptokinase (not significantly different) 2
• Any stroke: 1.6% vs 1.2-1.4% for streptokinase 2
• Combined mortality/nonfatal stroke was 1.0% lower with fibrin-specific agents 2

Real-World Asian Population Data

A 2022 propensity-matched study (n=718) directly comparing streptokinase versus tenecteplase in an Asian population found no significant differences in major bleeding outcomes 3:

• Major bleeding: Streptokinase 1.1% vs Tenecteplase 0.9% (p=0.624)
• Intracranial hemorrhage: Streptokinase 0.9% vs Tenecteplase 0.3% (p=0.624)
• Ischemic stroke: Comparable between groups

However, streptokinase had significantly higher rates of hypotension and allergic reactions 3.

Critical Clinical Considerations

Important caveats about bleeding risk:

• Age >75 years: In the elderly subgroup, stroke rates were actually numerically higher with fibrin-specific agents (4.0%) versus streptokinase (2.8-3.2%), though combined mortality/stroke outcomes remained similar 2
• Absolute contraindications apply equally to both agents: any prior intracranial hemorrhage, severe uncontrolled hypertension (SBP >180 or DBP >110 mmHg), recent stroke within 3 months 1
• Rare but catastrophic complications can occur with tenecteplase, including simultaneous intracranial and spinal hemorrhage, even without pre-existing vascular anomalies 4

Practical Algorithm for Agent Selection

Choose tenecteplase when:

• Age <75 years
• No history of prior stroke
• Blood pressure controlled <180/110 mmHg
• Weight-based dosing feasible (30-50 mg based on weight) 1

Consider streptokinase only when:

• Tenecteplase unavailable (though streptokinase is no longer available in the United States) 1
• Cost constraints in resource-limited settings
• Patient has demonstrated prior tolerance

Avoid both agents when:

• Primary PCI achievable within appropriate time windows
• Any absolute contraindications present
• ST-segment depression only (risk of hemorrhagic stroke outweighs benefit) 1

Dosing Specifics Matter for Safety

Tenecteplase's single weight-based bolus (30-50 mg over 5 seconds) offers practical advantages over streptokinase's 60-minute infusion, reducing medication errors and allowing faster transfer to PCI-capable facilities 1. This simplified administration may indirectly improve safety by reducing time to definitive care.

The evidence consistently supports tenecteplase as having equivalent or superior bleeding safety compared to streptokinase, with the added benefits of better efficacy, ease of administration, and lack of immunogenicity concerns.