PPACK Dihydrochloride is the dihydrochloride form of its active component PPACK (D-Phenylalanyl-L-prolyl-L-arginine chloromethyl ketone), a potent, selective, and irreversible inhibitor of thrombin that inhibits human α-thrombin with inhibition constant (Ki: 0.24 nM).

PPACK covalently binds to the specific active-site Ser of thrombin and cross-links with His57 at the binding site forming a tetrahedral PPACK-thrombin complex. The complex further binds to and saturates the high-affinity functional thrombin receptors eventually leading to the inhibition of thrombin activation. PPACK is currently being investigated as an anti-coagulant to prevent blood coagulation. Study results show that PPACK is able to dose-dependently inhibit thrombin-induced platelet accumulation.