Protamine is a drug that reverses the anticoagulant effects of heparin by binding to it.

Protamine is isolated from the sperm of various fish, and is a highly cationic peptide. It binds to heparin to form a stable ion pair which does not have anticoagulant activity. This complex is then removed and broken down by the reticuloendothelial system.

Dosage for heparin reversal is 1mg Protamine sulfate i.v. for every 100 IU of active heparin. It causes significant histamine release resulting in hypotension and bronchoconstriction, and also causes pulmonary hypertension. Infusion should be slow to minimise these side effects. In large doses, protamine itself has some anticoagulant effect.

It is also used in gene transfer and protein purification.

Reference

• Sigma

Antidotes | Pharmacologic agents