title: Severe bleeding in two patients due to increased sensitivity of factor IX activity to phenprocoumon therapy.
abstract: Two male patients with severe and recurrent bleeding episodes under phenprocoumon therapy are reported. Both patients exhibited a strong decrease of their factor IX activities below 1% of normal, whereas the activities of the vitamin K-dependent factors prothrombin, VII, and X were found to be within or above the expected therapeutic ranges of 20-40%. Upon removal of phenprocoumon and substitution with vitamin K, the factor IX activities increased to 85% and 55%, respectively. Reexposition to phenprocoumon in one patient confirmed the rapid and selective decrease of the factor IX activity. These findings provide the first report of an abnormally high sensitivity of factor IX activity to oral anticoagulant therapy.
authors.affiliation: Institute of Experimental Hematology and Transfusion Medicine, University of Bonn, Germany.
authors.forename: E M
authors.initials: EM
authors.lastname: Quenzel
authors.forename: H J
authors.initials: HJ
authors.lastname: Hertfelder
authors.forename: J
authors.initials: J
authors.lastname: Oldenburg
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D005164:Factor IX / Q000187:drug effects / Q000502:physiology*; D006470:Hemorrhage / Q000139:chemically induced / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010644:Phenprocoumon / Q000009:adverse effects / Q000627:therapeutic use*; D019106:Postoperative Hemorrhage / Q000139:chemically induced
chemical_list: D000925:Anticoagulants; D005164:Factor IX; D010644:Phenprocoumon