Group C Thrombolytic Agents: Mechanism and Types

Thrombolytic Agents Overview

• Thrombolytic agents are drugs used to dissolve blood clots, critical in treating conditions where ischemia can be life-threatening.
• The primary objective is to restore blood flow in blocked vessels by enhancing the breakdown of blood clots.
• They act by converting plasminogen, a proenzyme, into plasmin, the active enzyme responsible for clot lysis.

Types of Thrombolytic Drugs

• Non-fibrin Specific

  • Streptokinase: Affordable and effective, it is widely used globally but has a lower efficacy than alteplase and carries a reduced risk of intracranial hemorrhage.
  • Anistreplase: A complex of streptokinase and plasminogen that functions without requiring circulating plasminogen. High antigenicity is a notable drawback.
  • Urokinase: Commonly used for occluded catheters and peripheral thrombi, it is derived from human urine and can be produced recombinantly.

• Fibrin Specific

  • Alteplase: This recombinant tissue plasminogen activator (tPA) is the most frequently used fibrinolytic for treating acute cardiovascular events, with a short plasma half-life of 4-6 minutes.
  • Reteplase: A second-generation tPA that acts more quickly with a lower bleeding risk. It binds less strongly to fibrin, facilitating greater diffusion through clots.
  • Tenecteplase: Popular across the USA, Canada, and Europe, it has comparable efficiency to alteplase but presents a lower risk of non-cerebral bleeding.

Indications for Thrombolytics

• Acute myocardial infarction
• Acute ischemic stroke
• Peripheral artery occlusion
• Pulmonary embolism
• Deep venous thrombosis

Contraindications for Thrombolytics

• Active internal bleeding
• Recent intracranial trauma or tumors
• Cerebral hemorrhagic stroke
• History of cerebrovascular disease
• Major surgeries within the last two weeks
• Active peptic ulcers
• Diabetic retinopathy
• Pregnancy

Adverse Effects

• Common adverse effects include bleeding, hypotension, allergic reactions, angioedema, anaphylactic shock, and reperfusion arrhythmias, particularly during acute myocardial infarction.
• Streptokinase has the highest antigenicity, leading to frequent allergic reactions and hypotension.

Monitoring Requirements

• Continuous neurologic and cardiovascular assessment is necessary during and after thrombolytic therapy.
• Blood pressure should be monitored every 15 minutes initially, then every 30 minutes for 6 hours, and hourly for 16 hours thereafter.
• Immediate cessation of therapy is required if neurologic deterioration occurs, followed by an emergency CT scan.
• Cardiac monitoring is essential due to potential reperfusion arrhythmias.

Test your knowledge on thrombolytic agents, their mechanism of action, and types. Learn how they work to restore blood flow in occluded vessels and prevent ischemia. Identify the different types of thrombolytic drugs and their uses.