“…[14][15][16][17]33,35,[37][38][39] During the period 1955 to 1960, several groups of investigators found hirudin to be a specific inhibitor of thrombin. 40,41 Because of its remarkable specificity to thrombin, hirudin was used as a reagent in biochemical studies on the action of thrombin. Despite the high cost and labor associated with isolation and purification procedures, Markwardt and coworkers performed most of the basic biochemical and pharmacologic studies on natural hirudin.…”