Thrombolysis
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Thrombolysis is the breakdown (lysis) by pharmacological means, of blood clots. It is colloquially referred to as clot busting for this reason. It works by stimulating fibrinolysis by plasmin through infusion of analogs of tissue plasminogen activator, the protein that normally activates plasmin.
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Agents
Thrombolysis requires the use of thrombolytic drugs, which are either derived from Streptomyces spp. or (more recently) the effect of recombinant technology, where human activators of plasminogen (e.g. tissue plasminogen activator, tPA) are manufactured by bacteria.
Some commonly used thrombolytics are
- streptokinase
- urokinase
- alteplase (recombinant tissue plasminogen activator or rtPA).
Principles
Formation of blood clots lies at the basis of a number of serious diseases (see below). By breaking down the clot, the disease process can be arrested, or the complications reduced. While other anticoagulants (such as heparin) decrease the "growth" of a clot, thrombolytic agents actively reduce the size of the clot.
All thrombolytic agents work by activating the enzyme plasminogen, which clears the cross-linked fibrin mesh (the backbone of a clot). This makes the clot soluble and subject to further proteolysis by other enzymes, and restores blood flow over occluded blood vessels.
Uses
Diseases where thrombolysis is used:
Contraindications
These are contraindicated in bleeding disorders, active bleeding and when there has been recent surgery. Diabetic retinopathy is a relative contraindication.