Bivalirudin is a synthetic 20 amino acid peptide rationally designed based on structural studies of hirudin, a naturally occurring anticoagulant. Bivalirudin is sold under the brand name Angiomax and is indicated for use as an anticoagulant in patients with unstable angina undergoing percutaneous transluminal coronary angioplasty (PTCA). It is intended for use with aspirin and has been studied only in patients receiving concomitant aspirin. Bivalirudin directly inhibits thrombin by binding simultaneously to its active catalytic site and its substrate recognition site.