Phenindione

Phenindione is an anticoagulant, a type of medication that prevents or reduces coagulation of blood, prolonging the clotting time. It is a second-line treatment used only when other anticoagulants like warfarin or heparin are not suitable.

Pharmacology

Phenindione works by inhibiting the synthesis of vitamin K dependent clotting factors in the liver. These factors include II, VII, IX, and X, and the anticoagulant proteins C and S. The inhibition is achieved by the competition of phenindione with vitamin K for the same binding site on the enzymes that catalyse the carboxylation of these clotting factors.

Medical Uses

Phenindione is used in the prevention and treatment of thromboembolic disease such as stroke, myocardial infarction, and deep vein thrombosis. It is also used in patients with artificial heart valves to prevent clot formation.

Side Effects

The most common side effect of phenindione is bleeding. Other side effects include allergic reactions, hepatitis, and jaundice. Rarely, it can cause skin necrosis or gangrene.

Contraindications

Phenindione is contraindicated in patients with known hypersensitivity to the drug, in those with severe liver or kidney disease, and in pregnant women due to the risk of fetal bleeding.

Interactions

Phenindione can interact with many other drugs, including other anticoagulants, antibiotics, and drugs that affect liver enzymes. It is important to monitor the INR (International Normalized Ratio) regularly in patients taking phenindione to ensure the dose is correct.

See Also

• Anticoagulant
• Warfarin
• Heparin
• Vitamin K