Which of the following thrombolytic agents is a non-fibrin-selective plasminogen activator?

Explanation

## Classification of Thrombolytics **Key Point:** Thrombolytic agents are classified based on their fibrin selectivity — a critical determinant of their bleeding risk and clinical efficacy. ### Fibrin-Selective vs Non-Fibrin-Selective | Agent | Type | Mechanism | Fibrin Selectivity | Bleeding Risk | |-------|------|-----------|-------------------|---------------| | **Alteplase (tPA)** | Recombinant | Tissue plasminogen activator | High | Lower systemic fibrinolysis | | **Urokinase** | Non-recombinant | Direct plasminogen activator | **Low (non-selective)** | **Higher systemic fibrinolysis** | | **Tenecteplase (TNK-tPA)** | Recombinant | Modified tPA | High | Lower systemic fibrinolysis | | **Reteplase (r-PA)** | Recombinant | Deletion mutant of tPA | Moderate–High | Intermediate | | **Streptokinase** | Bacterial | Indirect activator | Low (non-selective) | Highest | **High-Yield:** Urokinase is a **non-fibrin-selective** plasminogen activator — it activates plasminogen in the circulation as well as at the thrombus surface, leading to systemic fibrinolysis and greater risk of bleeding complications. **Clinical Pearl:** Fibrin-selective agents (alteplase, tenecteplase, reteplase) preferentially activate plasminogen bound to fibrin, minimizing systemic fibrinolysis and reducing bleeding risk — this is why they are preferred in acute MI and acute ischemic stroke. **Mnemonic:** **FAST agents** = Fibrin-selective Activators: alteplase (tPA), Streptokinase (actually non-selective, exception), Tenecteplase, Reteplase. Urokinase and streptokinase are the **non-selective outliers**.