Pharm 101: Thrombolytic agents

Classes

Two major classes: t-PA (tissue plasminogen activator) and streptokinase


Tissue Plasminogen Activator (tPA)
  • Naturally occurring enzyme that directly converts plasminogen to plasmin
  • Plasmin is the major fibrinolytic enzyme, digesting fibrin
  • tPA preferentially activates plasminogen bound to fibrin by several hundred fold therefore is considered to be clot specific, and initiates local fibrinolysis
  • Recombinant human t-PA: alteplase, reteplase has a short half-life (5 minutes), therefore heparin is an essential adjunct
  • Tenectaplase is a mutant form of t-PA with a longer half-life and can be given as an IV bolus

Streptokinase
  • Not an enzyme itself, but a protein synthesised by streptococci
  • Combines with plasminogen to form an enzymatic complex that catalyses conversion of plasminogen to plasmin
  • Long half-life means that heparin is not required (may increase bleeding risk)
  • Prior streptococcal infection may result in antibodies that cause fever, allergic reactions and therapeutic resistance
  • Not indicated in acute ischaemic stroke due to increased bleeding risk

Clinical uses
  • STEMI
  • Unstable PE
  • Acute ischaemic stroke
  • Severe DVT

Adverse effects
  • Haemorrhage:
    • Intracerebral haemorrhage
    • GI bleeding
    • Previous surgery/wounds

Further reading

References
  • Katzung BG. Basic & Clinical Pharmacology. 14th ed. United States of America: McGraw-Hill Education; 2018. 611-619 p.

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MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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