Thrombolytics (tPA, Streptokinase, Urokinase)

Summary

Thrombolytics are a class of drugs that break down blood clots. They include tPA or the -teplase drugs, in addition to urokinase and streptokinase. Thrombolytics function by cleaving plasminogen into plasmin, which then dissolves the fibrin meshwork holding blood clots together. Thrombolytics are helpful for patients with ischemic stroke and ST-elevated myocardial infarction who present soon after their symptoms begin, and in patients with life-threatening pulmonary embolisms. However, these drugs are not without risks as thrombolytics can cause major bleeding. In severe bleeds, the action of thrombolytics can be reversed by tranexamic acid and aminocaproic acid.

Key Points

• Thrombolytics (Fibrinolytics)
  • Drug Names
    • Alteplase
      • Also known as tissue plasminogen activator (tpA)
    • Reteplase
    • Tenecteplase
    • Streptokinase
    • Urokinase
  • Mechanism
    • Dissolve clots (thrombi) by activating plasminogen to form plasmin
      • Plasmin cleaves fibrin (fibrinolysis) holding clots together
      • Alteplase and recombinant tpA drugs (reteplase, tenecteplase) are clot-specific and act only on fibrin-bound plasminogen
      • Streptokinase and urokinase are not clot-specific and activate all circulating plasminogen (including that bound to clots)
  • Clinical Use
    • Dissolution of clots/thrombi
      • Ischemic stroke within 3-4.5 hours
      • ST-elevation MI when stenting (PCI) is not available
        • Fibrinolytic drugs are used for treatment of acute myocardial infarction. They are most effective when used within six hours of onset of ST elevation myocardial infarction (Ml). Use of fibrinolytic drugs in properly selected patients of acute ST elevation Ml decreases mortality significantly.
      • Life-threatening pulmonary emboli
  • Laboratory Findings
    • Increased PT and PTT
      • Due to clot dissolution and active cleavage of fibrin
  • Adverse Effects
    • Bleeding
      • High bleeding risk, and should be avoided in patients with risk of intracranial bleeding, recent surgery, severe hypertension, or recent bleeding events
  • Reversal
    • Aminocaproic acid
    • Tranexamic acid