What is the route of administration of thrombin?

The route of administration of thrombin is local infiltration. It should be applied on the surface of bleeding tissue.
Medical thrombin is a protein substance produced through a conversion reaction in which prothrombin of bovine origin is activated by tissue thromboplastin in the presence of calcium chloride. Thrombin requires no intermediate physiological agent for its action. It clots the fibrinogen of the blood directly.

Thrombin also known as factor IIa is a serine protease that converts fibrinogen into fibrin in blood coagulation. The precursor of thrombin is prothrombin which is an inactive zymogen, is one of the several coagulation proteins containing γ‐carboxyglutamic acid which need vitamin K to be active.