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Protamine (Protamine Sulfate) - Description and Clinical Pharmacology


For Intravenous Use


Protamines are simple proteins of low molecular weight that are rich in arginine and strongly basic.  They occur in the sperm of salmon and certain other species of fish.

Protamine sulfate occurs as fine white or off-white amorphous or crystalline powder.  It is sparingly soluble in water.  The pH is between 6.0 and 7.0.  The cationic hydrogenated protamine at a pH of 6.8 to 7.1 reacts with anionic heparin at a pH of 5.0 to 7.5 to form an inactive complex.

Protamine Sulfate Injection, USP is a sterile, isotonic solution of protamine sulfate.  It acts as a heparin antagonist.  It is also a weak anticoagulant.

Each mL contains: Protamine sulfate 10 mg; sodium chloride 9 mg; Water for Injection q.s.  Sulfuric acid and/or dibasic sodium phosphate (heptahydrate) may have been added for pH adjustment.

The preparation is preservative free.

Protamine sulfate is administered intravenously.


When administered alone, protamine has an anticoagulant effect.  However, when it is given in the presence of heparin (which is strongly acidic), a stable salt is formed and the anticoagulant activity of both drugs is lost.

Protamine sulfate has a rapid onset of action.  Neutralization of heparin occurs within five minutes after intravenous administration of an appropriate dose of protamine sulfate.  Although the metabolic fate of the heparin-protamine complex has not been elucidated, it has been postulated that protamine sulfate in the heparin-protamine complex may be partially metabolized or may be attacked by fibrinolysin, thus freeing heparin.

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