In a 73-year-old amitriptyline-treated patient with major depression,
an additional oral anticoagulant therapy with phenprocoumon was requir
ed because of an acute lower extremity deep vein thrombosis. As a stea
dy state Quick evaluation within the therapeutic range was first possi
ble after discontinuation of the amitriptyline medication, a drug-drug
interaction between the two above mentioned substances can be suggest
ed.