title: Protein C response to induction and withdrawal of oral anticoagulant treatment.
abstract: Protein C activity and antigen levels have been related to clotting activities of factors VII and X during the induction and withdrawal periods of oral anticoagulant treatment. Both factor VII and protein C activities fell rapidly during induction but factor VII showed a more rapid and much more marked depression than protein C. In contrast, reductions in factor X were much slower. Protein C antigen, although depressed rapidly at the initiation of treatment, did not subsequently fall to the same degree as protein C activity. The ratio of activity to antigen became progressively smaller. On discontinuation there was a reversal of the pattern but with two important differences. Firstly, there was evidence of an excessive rise ('rebound') of factor VII compared with the steady state levels in these patients; and secondly there was a surprisingly slow return of protein C to normal levels after the oral anticoagulant was withdrawn (levels were still below normal on day 4). These observations lend support to gradual withdrawal of oral anticoagulants after a period of long-term administration. The results suggest that after discontinuation of long-term anticoagulants patients may have increased coagulability up to four days.
mesh_terms: D000074:Acenocoumarol / Q000008:administration & dosage; D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage*; D001779:Blood Coagulation Factors / Q000032:analysis; D006801:Humans; D011486:Protein C / Q000378:metabolism*; D013375:Substance Withdrawal Syndrome / Q000097:blood*
chemical_list: D000925:Anticoagulants; D001779:Blood Coagulation Factors; D011486:Protein C; D000074:Acenocoumarol