Thrombolytic therapy is a treatment option used in acute ischemic stroke to dissolve blood clots and restore blood flow to the affected area of the brain.
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The primary medication used for thrombolytic therapy in acute ischemic stroke is tissue plasminogen activator (tPA), specifically recombinant tissue plasminogen activator (rtPA). The mechanism of action of tPA involves the conversion of plasminogen to plasmin, which then breaks down fibrin, the main component of blood clots. Here’s how it works:
1. **Tissue Plasminogen Activator (tPA)**:
– **Mechanism of Action**: tPA is a serine protease that activates plasminogen, a precursor molecule found in blood clots, into plasmin. Plasmin is a potent enzyme that degrades fibrin, the structural protein of blood clots, leading to their dissolution or lysis.
– **Effect**: By promoting fibrinolysis, tPA helps break down the blood clot causing the ischemic stroke, restoring blood flow to the affected area of the brain and potentially preventing or minimizing neurological damage.
– **Administration**: tPA is administered intravenously as soon as possible after the onset of symptoms of acute ischemic stroke, typically within the first 4.5 hours, although the window for treatment may vary based on individual factors and guidelines.
2. **Other Thrombolytic Agents**:
– **Streptokinase**: Although less commonly used than tPA, streptokinase is another thrombolytic agent that functions by activating plasminogen and promoting fibrinolysis. It is not typically used for acute ischemic stroke due to its higher risk of allergic reactions and bleeding complications compared to tPA.
– **Tenecteplase**: Tenecteplase is a modified form of tPA that has a longer half-life and higher fibrin specificity, making it potentially more effective and easier to administer than tPA. However, its use in acute ischemic stroke is still investigational and not yet widely adopted.
Thrombolytic therapy with tPA is a time-sensitive intervention that carries risks of bleeding complications, particularly intracranial hemorrhage, which must be carefully weighed against potential benefits. Therefore, prompt recognition of stroke symptoms, rapid evaluation, and timely administration of thrombolytic therapy are crucial for optimizing outcomes in patients with acute ischemic stroke. Thrombolytic therapy is generally reserved for patients with ischemic stroke caused by a large vessel occlusion and without contraindications to treatment.