Fluindione

Fluindione is a synthetic anticoagulant belonging to the indanedione class of drugs. It is structurally related to phenindione and diphenadione. Fluindione functions as a vitamin K antagonist, inhibiting the synthesis of vitamin K-dependent clotting factors, namely factors II, VII, IX, and X, as well as the anticoagulant proteins C and S. This mechanism of action leads to a reduction in the blood's ability to clot.

Historically, fluindione was used for the prophylaxis and treatment of thromboembolic disorders, such as deep vein thrombosis and pulmonary embolism, and to prevent clot formation in patients with artificial heart valves or atrial fibrillation. Its therapeutic effect is monitored by measuring the prothrombin time (PT), often expressed as the International Normalized Ratio (INR).

However, the use of fluindione has significantly declined due to a number of factors. It has a narrow therapeutic index and a variable patient response, making dose adjustment challenging. Furthermore, the risk of adverse effects, including bleeding complications and hypersensitivity reactions such as skin rashes and hepatitis, has led to its replacement by other anticoagulant medications with more favorable safety profiles and predictable pharmacokinetics, such as warfarin and the direct oral anticoagulants (DOACs). Consequently, fluindione is rarely prescribed in many parts of the world today.