thrombolytic

A thrombolytic is the chemical equivalent of a drain-clearing solvent for blood vessels: it dissolves a clot that is already blocking flow. While an anticoagulant or antiplatelet only stops new clots from forming, a thrombolytic actively breaks down an existing clot, reopening an artery so blood can reach starving tissue again.

Thrombolytics activate the body's own clot-dissolving system, fibrinolysis. They convert the inactive protein plasminogen into plasmin, an enzyme that chops up the fibrin mesh holding a clot together. Agents include tissue plasminogen activators such as alteplase and tenecteplase, and the older streptokinase. They are used in carefully selected emergencies: certain heart attacks (when timely angioplasty is unavailable), acute ischaemic stroke within a tight time window, and massive pulmonary embolism with shock.

Because they dissolve clots everywhere, not just the harmful one, the dominant risk is severe bleeding, most feared being bleeding into the brain. This makes timing and patient selection critical: they only help if given soon after symptoms start, and they are contraindicated in anyone with recent surgery, active bleeding, uncontrolled hypertension or a prior haemorrhagic stroke. The decision weighs the benefit of reopening a vessel against the danger of catastrophic haemorrhage.