Fibrinolytic Drugs: Definition, Classification, Mechanism, Uses, Adverse Effects, and Contraindications

1. First-Generation Fibrinolytics

• Streptokinase: A bacterial enzyme that indirectly activates plasminogen.
• Urokinase: A human-derived enzyme that directly converts plasminogen to plasmin.

2. Second-Generation Fibrinolytics

• Tissue Plasminogen Activator (t-PA): A naturally occurring enzyme targeting fibrin-bound plasminogen, enhancing clot specificity.
• Recombinant Tissue Plasminogen Activator (r-tPA): Includes drugs like alteplase, reteplase, and tenecteplase.

Fibrinolytics promote the conversion of plasminogen to plasmin, which degrades fibrin and dissolves blood clots. This action restores blood flow by breaking down the clot:

• Streptokinase and urokinase: Act throughout the bloodstream by activating plasminogen.
• t-PA and r-tPA: Target fibrin-bound plasminogen within clots, minimizing systemic effects.

• Myocardial Infarction (MI): Used to reopen occluded coronary arteries in the early stages.
• Acute Ischemic Stroke: Early administration helps dissolve cerebral artery clots and restores brain perfusion.
• Pulmonary Embolism (PE): Indicated in life-threatening cases for clot dissolution in the lungs.
• Deep Vein Thrombosis (DVT): In some cases, fibrinolytics are used to dissolve clots in deep veins.

• Bleeding: Risk of bleeding, especially intracranial and gastrointestinal hemorrhage.
• Allergic Reactions: Particularly with streptokinase, due to its bacterial origin.
• Reperfusion Arrhythmias: Sudden blood flow restoration can lead to arrhythmias, especially post-MI.
• Hypotension: Commonly associated with streptokinase.

1. Absolute Contraindications

• Active internal bleeding or known bleeding disorders
• Recent intracranial hemorrhage or stroke (within 3 months)
• Known cerebral vascular malformations
• Recent head trauma or major surgery (within 2–3 weeks)

2. Relative Contraindications

• Pregnancy
• Uncontrolled severe hypertension
• Peptic ulcer disease
• Recent invasive procedures