definiens: means Bivalirudin, being a highly specific and reversible direct thrombin inhibitor, which operates by speci fie binding to both the catalytic site and to the anion - binding exosite of circulating and clot - bound thrombin . The active substance is a synthetic, twenty ( 20)-amino acid peptide, whose chemical name is D - phenylalanyl - Lprolyl - Larginyl - L - prolyl - glycyl - glycyl - glycyl - glycyl - L - asparagyl - gl ycyl - L - aspartly - L - phen ylalanyl - L - glutamyl - L - glutam yl - isoleucyl - L - prolyl - L - glutamyl - L - glutamyl - L - tyrosyl - L - leucine - trifluoracetate ( salt ) hydrate . Its molecular weight is 218.19 daltons ( anhydrous free base peptide )