The effect of a low molecular weight heparin on coagulation parameters in healthy cats.

The low molecular weight heparin (LMWH), dalteparin sodium, was administered subcutaneously (100 IU/kg) to 8 healthy cats twice daily for 13 doses. Anti-activated factor X (anti-Xa) activity was measured prior to administration (time 0), and 4, 6, 8, and 12 h after the 1st dose, 4 h after administration of the 3rd dose, and at 4, 6, 8, and 12 h after the last dose. Four cats developed measurable anti-Xa activity 4 h following a single dose, returning to baseline by 6 h. Anti-Xa activity was not detected at any time point in 4 cats. Prothrombin time (PT), activated partial thromboplastin time (APTT), and antithrombin (AT) concentrations were unaffected by LMWH administration. Dalteparin, at 100 IU/kg SC, did not achieve anti-Xa activity in 4 out of 8 cats and failed to maintain anti-Xa activity beyond 4 h in the other 4 healthy cats.