Low molecular weight heparin (KABI 2165, Fragmin): pharmacokinetics after intravenous and subcutaneous administration in human volunteers

The pharmacokinetics of a low molecular weight heparin (LMWH) with a mean mw of 4000-6000 D (KABI 2165, Fragmin) was studied in 6 healthy volunteers after intravenous (iv) and subcutaneous (sc) administration of 120 U (anti FXa)/kg. The half-life in plasma of the anti FXa activity after iv injection was 119 +/- 17 min, the volume of distribution (Vd) 3.4 +/- 0.5 1 and the total clearence 20.5 +/- 2.5 ml/min. The maximal anti FXa activity determined 3 min after iv bolus injection amounted to 2.2 +/- 0.3 U (anti FXa)/ml with a corresponding increase of the APTT from 31 +/- 7 sec to 113 +/- 35 sec. The elimination of the anti FXa activity was a monoexponential first order process. After sc administration the plasma half-life of the anti FXa activity was longer than after iv injection, 228 +/- 40 min, corresponding to the absorption rate thus found to be the rate limiting step. After sc administration the peak was reached after 4 hours (0.6 +/- 0.1 U (anti FXa)/ml; APTT increase 5 sec). The bioavailability after sc injection was calculated to be 87 +/- 6%. As a consequence of the high bioavailability and long T1/2 of the anti FXa activity, Fragmin administered sc seems to induce adequate levels of heparin-like activity making this regimen worth further investigation as an alternative for the treatment of deep venous thrombosis.