Protamine sulfate is a drug that reverses the anticoagulant

Anticoagulant

An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

 effects of heparin

Heparin

Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...

 by binding to it.

Protamine was originally isolated from the sperm of salmon and other species of fish but is now produced primarily through recombinant

Recombinant DNA

Recombinant DNA molecules are DNA sequences that result from the use of laboratory methods to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms...

 biotechnology. It is a highly cationic peptide. It binds to heparin to form a stable ion pair which does not have anticoagulant activity; on its own, protamine has a weak anticoagulant effect. The complex of heparin and protamine is then removed and broken down by the reticuloendothelial system

Reticuloendothelial system

"Reticuloendothelial system" is an older term for the mononuclear phagocyte system. The mononuclear phagocyte system consists primarily of monocytes and macrophages. The spleen is the largest unit of the mononuclear phagocyte system. The monocyte is formed in the bone marrow and transported by the...

.

Dosage

Dosage for heparin reversal is 1 mg protamine sulfate i.v. for every 100 IU of active heparin. In patients who are allergic to fish, it can cause significant histamine

Histamine

Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...

 release resulting in hypotension

Hypotension

In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

 and bronchoconstriction

Bronchoconstriction

Bronchoconstriction is the constriction of the airways in the lungs due to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. Bronchoconstriction can also be due to an accumulation of thick mucus....

, and also causes pulmonary hypertension

Pulmonary hypertension

In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...

. Infusion should be slow to minimize these side effects. In large doses, protamine itself has some anticoagulant effect.

Uses

Protamine sulfate is usually administered to reverse the large dose of heparin administered during certain surgeries, especially heart surgery. It is also used in gene transfer and protein purification. It is also used in tissue cultures as a crosslinker for viral transduction.