Fibrinolytics, also known as thrombolytic agents or clot-busting drugs, are a class of drugs that dissolve blood clots by breaking down fibrin, the structural protein of clots. They work by activating plasminogen to plasmin, which degrades fibrin and helps restore normal blood flow. These agents are commonly used in the treatment of conditions such as myocardial infarction (heart attack), ischemic stroke, and pulmonary embolism to prevent life-threatening complications caused by blood clots.
In general, venous thrombi are more susceptible to lysis by fibrinolytic agents compared to arterial thrombi, with recent thrombi responding more effectively. Fibrinolytics have minimal impact on thrombi older than three days. The primary fibrinolytic drugs include:
- Streptokinase
- Urokinase
- Alteplase (rt-PA)
- Reteplase
- Tenecteplase
Streptokinase (Stk)
Streptokinase is a thrombolytic enzyme derived from Streptococcus bacteria. It works by activating plasminogen to form plasmin, which helps dissolve blood clots. It is used clinically to treat conditions like myocardial infarction (heart attack), deep vein thrombosis, and pulmonary embolism.
Urokinase
Urokinase is a thrombolytic enzyme that activates plasminogen to convert it into plasmin, which helps break down blood clots. Originally isolated from human urine, it is now commercially produced from cultured human kidney cells. Naturally produced in the kidneys, urokinase has been used clinically to treat conditions such as pulmonary embolism and deep vein thrombosis. However, due to the development of more effective fibrinolytic agents, its clinical use has largely been discontinued.
Alteplase (Recombinant Tissue Plasminogen Activator, rt-PA)
Alteplase is a recombinant tissue plasminogen activator (rtPA) used as a thrombolytic agent. It works by converting plasminogen into plasmin, which helps dissolve blood clots. Alteplase is primarily used in the treatment of acute ischemic stroke, myocardial infarction (heart attack), and pulmonary embolism.
Tenecteplase
Tenecteplase is a recombinant tissue plasminogen activator (rtPA) that acts as a thrombolytic agent. It works by converting plasminogen into plasmin, which breaks down blood clots. Tenecteplase is primarily used for the treatment of acute myocardial infarction (heart attack) and has a longer half-life and greater fibrin specificity compared to Alteplase.
Uses of Fibrinolytics
Fibrinolytics, also known as thrombolytic agents, are drugs that help dissolve blood clots by breaking down fibrin, the structural component of a clot. They are primarily used in the treatment of conditions where blood clots obstruct normal circulation. Some key uses include:
Acute Myocardial Infarction (Heart Attack): Used to dissolve thrombi in coronary arteries to restore blood flow and prevent heart muscle damage.
Common fibrinolytics: Alteplase, Reteplase, Tenecteplase.
Ischemic Stroke: Administered within 3–4.5 hours of symptom onset to dissolve clots in cerebral arteries.Alteplase (tPA) is the most commonly used fibrinolytic for stroke.
Pulmonary Embolism (PE): Used in severe cases of PE with hemodynamic instability (massive PE) to rapidly dissolve clots in pulmonary arteries.
Deep Vein Thrombosis (DVT): Occasionally used in severe cases to prevent post-thrombotic complications and venous insufficiency.
Catheter Clearance (Central Venous Catheter or Dialysis Catheter Occlusion): Small doses of fibrinolytics, such as Alteplase, are used to clear blocked central venous catheters.
Peripheral Arterial Thrombosis and Limb Ischemia: Used to restore blood flow in occluded peripheral arteries, preventing limb amputation.
Blocked Prosthetic Heart Valves: In some cases, fibrinolytics are used to dissolve thrombi that obstruct mechanical heart valves.
