Clinical pharmacology of intravenously administered recombinant desulfatohirudin (CGP 39393) in healthy volunteers.

Clinical pharmacology of the intravenously administered recombinant desulfatohirudin CGP 39393 was investigated in 47 healthy volunteers in a multicenter study. Mean peak concentrations after bolus injections of 0.1, 0.3, 0.5, and 1.0 mg/kg were 154, 443, 764, and 1,691 nmol/L, respectively. Intravenous infusions of 0.1 mg/kg/h for 6 h and of 0.2 and 0.3 mg/kg/h for 6 h and 72 h resulted in mean steady-state levels of 78, 227, and 312 nmol/L. Elimination was multiexponential and dose independent. Concordant pharmacokinetic parameters were obtained from both i.v. bolus and infusion experiments (overall average total plasma clearance, 2.20 ml/min/kg; mean residence time, 2.12 h; volume at steady state, 0.27 L/kg). Thrombin inhibition by CGP 39393 was demonstrated ex vivo by the thrombin chromogenic assay (TCA), by activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT). Following a parabolic function APTT doubled and quadrupled at CGP 39393 concentrations of 100 and 1,000 nmol/L, respectively. Whereas TTs (bovine thrombin 3 or 6 IU/ml) were very sensitive to low CGP 39393 levels with unmeasurable clotting times at CGP 39393 concentrations greater than 30 and 60 nmol/L, PT was prolonged by a factor of only 1.3 above baseline at 300 nmol/L. APTT appears to be most suitable for monitoring the anticoagulant effect of CGP 39393 over a broad concentration range. The drug was well tolerated without clinically relevant bleeding episodes or other adverse events.