PROTAMINE

​

Protamine is a small, highly basic protein derived from fish sperm that is used primarily to reverse the effects of heparin, an anticoagulant drug.

 

Heparin is commonly administered during surgical procedures, particularly cardiovascular surgeries, to prevent blood clot formation and reduce the risk of thromboembolic events. However, it is crucial to neutralize the anticoagulant effect of heparin after the surgery or in cases of excessive bleeding.

 

This is where protamine becomes important. It binds to heparin, forming a stable complex that inactivates the anticoagulant properties of heparin, thus restoring normal blood clotting function.

 

Protamine is essential in managing the anticoagulation status of patients undergoing surgery, particularly those surgeries that require cardiopulmonary bypass or other invasive procedures. 

​

The mechanism of action of protamine involves its interaction with heparin, which leads to the neutralization of heparin's anticoagulant activity. Here are the main steps in protamine's mechanism of action:

​

1. Electrostatic interaction: Protamine is a cationic (positively charged) protein, while heparin is an anionic (negatively charged) glycosaminoglycan. Due to their opposite charges, protamine and heparin are attracted to each other, leading to the formation of electrostatic interactions.

2. Formation of a stable complex: The interaction between protamine and heparin results in the formation of a stable, inactive complex. The binding of protamine to heparin neutralizes the anticoagulant properties of heparin, as the heparin molecules are no longer available to bind and activate antithrombin III.

3. Restoration of normal blood clotting: Once heparin is neutralized by protamine, the coagulation cascade can proceed without the inhibitory effect of heparin, allowing blood clotting to return to its normal state.

​

​​

                                                                                         Key points about Protamine

​

• The only available agent to reverse unfractionated heparin.

 

• Protamine is a strongly alkaline polycationic low molecular weight protein found in salmon sperm.

 

• It can cause adverse reactions including anaphylaxis, acute pulmonary vasoconstriction, right ventricular failure, and hypotension.

 

• Excess protamine should be avoided when reversing heparin as it can contribute to coagulopathy.

 

• Patients with a history of past protamine exposure, fish allergy, vasectomy, and insulin-controlled diabetes are at increased risk of adverse reactions.

 

• Patients on NPH insulin are at increased risk of protamine reaction.

 

• NPH stands for neutral protamine Hagedorn.

 

​​

 

​​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

 

​​

​​