[Are salicoyl-like analgesics vitamin K antagonists? An interpretation of spontaneous subnormal Quick values]

Prolonged spontaneous prothrombin time values (subnormal Quick values of between 50--70%), such as are encountered frequently in the clinical laboratory, are discussed. The reason for these abnormal values may be traced in part to the ingestion of salicoyl-like analgesics. Acetylsalicylic acid must be considered a low-acting oral anticoagulant which behaves like a vitamin K antagonist. In connection with the frequent use of this substance its interference with the plasmatic blood coagulation system should be considered.