Effects of low-molecular-weight heparin on platelets as compared with commercial heparin.

Five subjects were injected with 5,000 IU of commercial heparin and low-molecular-weight heparin at an interval of 20 days after each injection. Both heparins produced the same platelet factor 4 release immediately after administration (commercial heparin 114.6 +/- 21.6 ng/ml, low-molecular-weight heparin 113.1 +/- 22.1 ng/ml). However, commercial heparin induced a more evident potentiating effect on ADP-induced platelet aggregation and was still present 60 min after injection. Low-molecular-weight heparin had a higher anti-Xa-specific activity than that determined by activated partial thromboplastin time. The opposite was true for the commercial preparation.