Thrombolytics: Nursing pharmacology

Thrombolytics, also called clot busters, are medications that break up clots, and are used for the short-term emergency management of thrombotic conditions, such as myocardial infarction, pulmonary embolism, ischemic stroke, and thrombosis of prosthetic heart valves and stents.

Now, thrombolytics are usually derived from enzymes involved in fibrinolysis, or the gradual degradation of the fibrin mesh. These include alteplase, reteplase, and tenecteplase, which are derived from tissue plasminogen activator, or tPA, through recombinant DNA technology, and act locally at the clot site.

Thrombolytics are given intravenously. Once in the blood, they act on a protein produced by the liver called plasminogen, and convert it into its active form called plasmin.

These medications directly bind to fibrin proteins in the clot and preferentially act on plasminogen trapped in the fibrin mesh, also called fibrin-bound plasminogen. The resulting plasmin then acts as a protease and cuts the fibrin into smaller pieces.

This allows the trapped red blood cells and platelets to float away, dissolving the clot.The main side effect of all thrombolytics is undue bleeding from other sites, including the injection site, gastrointestinal bleeds, and hemorrhagic stroke.

In severe cases, thrombolytic-associated bleeding can be treated with medications like aminocaproic acid, which acts by binding to plasminogen and plasmin, ultimately inhibiting their action on fibrin.

If aminocaproic acid fails, other transfusion products can be administered, such as platelets or coagulation factors in the form of fresh frozen plasma.