Pharmacology of hirudin: one hundred years after the first report of the anticoagulant agent in medicinal leeches.

One hundred years after its discovery hirudin, the selective thrombin inhibitor from medicinal leeches, has been brought into the focus of interest again. Advanced methods of peptide isolation and gene technology are expected to provide the opportunity to obtain pure hirudin in sufficient yield for therapeutic uses. Therefore, the present state of knowledge of this naturally occurring anticoagulant is reported.