Phenprocoumon

Phenprocoumon is an anticoagulant of the coumarin class, used to prevent and treat thrombosis and embolism. It is a vitamin K antagonist (VKA) similar to warfarin and is used particularly in some European countries. Phenprocoumon's anticoagulant effects are achieved by inhibiting the synthesis of vitamin K-dependent clotting factors, which are critical for blood clotting.

Mechanism of Action

Phenprocoumon works by inhibiting the enzyme vitamin K epoxide reductase. This inhibition blocks the regeneration of vitamin K1 epoxide, leading to a decrease in the synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, produced in the liver. These clotting factors are essential for the coagulation cascade, a series of steps involved in the formation of a blood clot. By reducing the production of these factors, phenprocoumon decreases the likelihood of clot formation.

Indications

Phenprocoumon is indicated for the prevention and treatment of:

• Venous thrombosis
• Pulmonary embolism
• Thromboembolic complications associated with atrial fibrillation
• Thromboembolic complications in patients with prosthetic heart valves

Pharmacokinetics

Phenprocoumon has a long half-life, ranging from 100 to 150 hours, which allows for once-daily dosing. Its anticoagulant effect is delayed until the active clotting factors are depleted, which may take several days. For this reason, an initial heparin treatment may be necessary to provide immediate anticoagulation.

Adverse Effects

The most significant risk associated with phenprocoumon therapy is bleeding. Other potential adverse effects include:

• Skin necrosis
• Purple toe syndrome
• Hepatic dysfunction
• Alopecia

Patients on phenprocoumon therapy require regular monitoring of their International Normalized Ratio (INR) to ensure that their blood remains within the therapeutic range, minimizing the risk of both thrombosis and bleeding.

Drug Interactions

Phenprocoumon's effectiveness can be affected by other medications, foods, and herbal supplements. Drugs that can increase phenprocoumon's anticoagulant effect and hence, the risk of bleeding include:

• Antibiotics
• Antifungals
• Antidepressants
• Nonsteroidal anti-inflammatory drugs (NSAIDs)

Conversely, drugs such as barbiturates and rifampicin can decrease its effect.

Contraindications

Phenprocoumon is contraindicated in patients with:

• Known hypersensitivity to phenprocoumon or any component of the formulation
• Hemorrhagic tendencies or blood dyscrasias
• Severe liver or kidney disease
• Pregnancy, particularly in the first and third trimesters

See Also

• Anticoagulant
• Vitamin K antagonist
• Warfarin
• Thrombosis
• Embolism