A preparation of a protein obtained from culture filtrates
of certain strains of haemolytic Streptococcus group C. It is a thrombolytic
agent which limits the clot formation.It has the property of combining with
human plasminogen to form plasminogen activator. Streptokinase, one of the
first such agents to be approved, causes
a systemic fibrinolytic state that can lead to bleeding problems.
How it was discovered?
The first thrombolytic, Streptokinase (SK) was discovered by
Dr William Smith Tillett in 1933 by sheer serendipity (By chance).His
observation was about haemolytic streptoccal agglutination in Human plasm test
tubes and not in Human serum test tubes.He hypotesized that this agglutination
was due to fibrinogen in plasma which is deficient in serum. Formely the
term Fibrolysin was used for
streptococcal fibrinolytic component which was then replaced by streptokinase
in 1945 by Christensen and Macleod. Now a days Christensen units represents its
potency.
How it acts?
During plug formation, the fibrinolytic pathway is locally activated. Plasminogen is enzymatically processed to plasmin (fibrinolysin) by plasminogen activators in the tissue Plasmin limits the growth of the clot and dissolves the fibrin network as wounds heal.
Streptokinase is an enzyme but when used as a thrombolytic it do not show enzymatic activity.Instead it binds to it forms an active one-to-one complex with plasminogen.
This enzymatically active complex converts uncomplexed plasminogen to the active enzyme plasmin In addition to the hydrolysis of fibrin plugs, the complex also catalyzes the degrada-tion of fibrinogen as well as clotting Factors V and VII
Altepase, Urokinase and streptokinase are same in action or not?
All belong to same category i.e. Thrombolytic agents but do not act by same mechaanism.Altepase act locally on fibrin to bring fibrolysis. While urokinase act by directly converting the plasminogen into plasmin which degrades the fibrin.Mechanism of action of streptokinase is mentioned above.
How potency of streptokinase is measured?
The potency of streptokinase is expressed in international units and preparations are assayed using the second International Standard (1989).
The Christensen unit is the quantity of streptokinase that will lyse a standard blood clot completely in 10 minutes and is equivalent to the international unit. The potency is not less than 510 international units per microgram of nitrogen.
Some important things which
should be considered before administeration?
Streptokinase is contraindicated
in the following.
- Existing or recent internal haemorrhages, all forms of decrease blood coagulability, in particular spontaneous fibrinolysis and extensive clotting disorders.
- Acute pancreatitis, severe liver or kidney damage.
- Recent implantation of vessel prosthesis
- Endocarditis or pericarditis
- Simultaneous treatment with oral anticoagulants (INR>1.3).
- Known haemorrhagic diathesis.
- Recent major operations
- Arteriovenous malformation or aneurysm.
- Recent cerebrovascular insults, intracranial or intraspinal surgery, recent head trauma
Some Important points about streptokinase to be memorized
- Streptokinase is antigenic; can cause hyper-sensitivity reactions and anaphylaxis, especially when used second time in a patient. Repeat doses are also less effective due to neutralization by antiodies. Fever is common, hypotension and arrhythmias are reported.
- Streptokinase infusion has been associated with the development of very severe low back pain, which resolves with-in a few minutes of stopping the infusion, and may be severe enough to warrant opioid analgesia.
- Drop-counting infusion pump should not be employed because it undergoes flocculation producing translucent fibres that affect the drop-forming mechanism so increas-ing the drop size.
4.Dantrolene! A Direct Skeletal muscle Relaxant
3. Improve your Knowledge about ampicillin
