EFFECT OF LOW-MOLECULAR-WEIGHT HEPARIN (TINZAPARIN) AND UNFRACTIONATED HEPARIN ON PLATELET-AGGREGATION

A low-molecular-weight heparin (LMWH), Tinzaparin, was compared with u nfractionated heparin (UFH) for their effects on platelet aggregation in vitro and ex vivo. Both heparins showed a dose-dependent proaggrega tory effect on ADP- and collagen-induced platelet aggregation in vitro , but LMWH was less potent. The differences in potency between Tinzapa rin and UFH depended on how the compounds were compared. The most pron ounced difference was found when molar concentrations were used for co mparison; the smallest was found when anti-IIa activity was compared. In the ex vivo part of the study, a significant enhancement of ADP-ind uced platelet aggregation was observed after i.v. administration of bo th Tinzaparin and UFH with no difference in potency. Subcutaneous admi nistration of Tinzaparin in two different doses did not have any effec t on platelet activity. In conclusion, Tinzaparin appears, like other LMWHs, to have less proaggregatory effect on platelets than UFH both i n vitro and ex vivo.