Drug Interactions involving Anticoagulants, Alcohols and Barbiturates

Abstract

A) DRUG INTERACTIONS WITH ORALANTICOAGULANTS

Vitamin K is essential for the synthesis of prothrombin and other clotting factors synthesized in the liver (l-actors VII, IX and X). Oral anticoagulants of the ooumarin and indanedione series arc competitive antagonists of vitamin Thus they are used to depress the blood prothrombin concentration to a point which is enough to prevent in- travascular clotting but not enough to produce spontaneous bleeding. This critical prothromhin level can he upset by the concurrent adniinistration of some drugs. Also if the dose of the anticoagulant required to produce the desired effect in at patient was determined when the patient was receiving another drug, withdrawal of this second drug may expose the patient to thedanger of spontancousthrombosis. Many drugs can interact with oral anticoagulants either to enhance or to reduce their activities.