What is a Thrombin Inhibitor?

A thrombin inhibitor interferes with the body’s ability to produce blood clots by binding to the enzyme thrombin and deactivating it. This enzyme is key to blood clot formation because it helps to create the binding agent, fibrin, attracts platelets to the site of the hemorrhage, and increases the body’s production of more thrombin. Thrombin also helps to keep blood clots from breaking up by increasing the effectiveness of fibrin. It may be necessary for a patient to use a thrombin inhibitor if he is at risk of stroke or other serious health problems due to the presence of blood clots.

There are three sites, an active site and two exosites, on a thrombin molecule that it uses to assist in the creation of blood clots. Thrombin attaches to fibrin along its active site and uses its two exosites to synthesize other enzymes. Antithrombin molecules, and drugs that utilize antithrombin to prevent blood clots, are unable to access thrombin once it has attached to fibrin. This gives a thrombin inhibitor medication an advantage over other types of medications because it can deactivate thrombin, using the active site, the exosites, or a combination of the two.

In some patients, when the risk of serious injury due to the formation of a blood clot is severe, deactivating free-floating thrombin is not enough. These patients benefit from the use of a thrombin inhibitor because drugs in this class deactivate thrombin within a blood clot as well as thrombin in the blood stream. The thrombin left active in the blood clot has the ability to create more thrombin, which can make the blood clot grow even larger. A thrombin inhibitor can prevent this from happening.

There are different types of thrombin inhibitor drugs available. Certain types are engineered to bind to thrombin on a single site, while others bind to it in two places. Some of the latter of these can be split in half after a short time, which renders the medication inactive. This allows for a short-lived thrombin inhibitor effect, which is beneficial to certain patients.

Blood clots may be dangerous for patients who have recently undergone major surgery on the hip or knee joints and for those who are at a high risk for stroke due to atrial fibrillation. Within these populations it may be necessary to inhibit the growth of blood clots even with the increased risk of bleeding. A thrombin inhibitor may be prescribed for patients for whom other types of anti-coagulants or anti-platelets are ineffective.