Thrombolytic therapy is used to dissolve clot in vivo. To break thrombi, these drugs degrade fibrin by activating plasminogen to form plasmin.

1. Streptokinase:

It is used in Thrombolytic therapy and is a protein and is synthesized by beta-haemolytic streptococci.

It is employed in the treatment of life-threatening venous thrombosis and in pulmonary embolism. It is given by intravenous infusion as a loading dose (2,50,000 units in 30 minutes) followed by 1,00,000  units per hour for 24—72 hours. During therapy, thrombin time should be closely monitored.

Intracoronary administration of streptokinase within 6 hours of an acute coronary thrombosis can restore flow in occluded artery and may reduce mortality.

2. Urokinase:

It is a proteolytic enzyme. It is derived from the human kidney and is present in urine. It is now prepared from tissue cultures of human renal cells. So it is non-antigenic.

It directly converts plasminogen into plasmin. It is given intravenously as a loading dose (3, 00,000 units) followed by 3,00,000 units per hour for 12 hours.

Recently a new recombinant pro-urokinase has been produced by recombinant DNA technology. It is more fibrin-selective because it is converted to urokinase on binding to fibrin. It is used in thrombosed arteriovenous shunts and for thrombolytic therapy in the eye.

3. Alteplase (tissue plasminogen activator; TPA):

It is also fibrinoselective and avoids systemic activation. It has been obtained from cultured human melanoma cells and by recombinant DNA technology. It is given in a dose of 100mg intravenously in 3 hours.

4. Anisolylated plasminogen-streptokinase activator is a complex of human plasminogen and streptokinase which has been made inactive by the introduction of panisolyl group.

In the blood, anisolyl group is removed by a hydrolytic deacylation process. It is given as a single injection intravenously in thrombolytic therapy over 4—5 minutes and the fibrinolytic activity is sustained for 4—6 hours.

Therapeutic Uses of Thrombolytic therapy

i. Multiple pulmonary emboli

ii. Central deep vein thrombosis

iii. Acute coronary thrombosis

iv. Peripheral arterial occlusion

Thrombolytic therapy Adverse Drug Reactions

• Bleeding

• Multiple micro-emboli from disintegrating the pre-existing thrombus

• Mild allergic reactions may occur with drugs containing streptokinase.

Thrombolytic therapy Contraindications

These drugs should not be used in the following conditions:

• Conditions having risk of bleeding

• Vascular aneurysm

• Endocardial thrombi

• Allergy to streptokinase