Marcoumar (Phenprocoumon)

Phenprocoumon is used to manage conditions related to abnormal blood clot formation.

• Deep vein thrombosis: prevents clot extension and recurrence in the legs.
• Atrial fibrillation: reduces risk of ischemic stroke by inhibiting clot formation.
• Orthopedic surgery: provides prophylaxis against postoperative venous thromboembolism.
• Pulmonary embolism: treats and prevents recurrence of emboli in the lungs.

• Phenprocoumon inhibits the enzyme vitamin K epoxide reductase, which is essential for recycling vitamin K. This blockade reduces the regeneration of active vitamin K, thereby decreasing the hepatic synthesis of the vitamin K‑dependent clotting factors II, VII, IX and X. The resulting deficiency impairs the coagulation cascade, producing an anticoagulant effect that limits thrombus formation.

Phenprocoumon may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Minor bleeding (e.g., gum or nosebleeds)
• Bruising or hematoma formation
• Nausea or abdominal discomfort
• Diarrhea

Serious or Rare Side Effects

• Severe hemorrhage (intracranial or gastrointestinal)
• Skin necrosis
• Allergic reactions such as rash, angioedema, or anaphylaxis

When prescribing Phenprocoumon, clinicians should observe several safety measures to minimize risk.

• Dose adjustment: individualize based on INR monitoring and patient response.
• Liver disease: avoid or use with caution in hepatic impairment.
• Renal impairment: monitor closely in patients with reduced kidney function.
• Concomitant anticoagulants: avoid combining with other anticoagulant agents unless specifically indicated.
• Pregnancy: contraindicated in pregnancy (Category X) due to teratogenic risk.
• Store at ambient temperature: keep tablets below 25 °C in the original pack, protect from moisture.

Phenprocoumon interacts with several medicines that can alter its anticoagulant effect.

Major Interactions (Avoid)

• Strong CYP2C9 inhibitors (e.g., fluconazole, amiodarone): markedly increase plasma levels, risk of bleeding.
• Antiplatelet agents (e.g., clopidogrel, aspirin): additive anticoagulant effect, may cause severe bleeding.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs): enhance bleeding tendency.

Moderate Interactions (Monitor Closely)

• CYP2C9 inducers (e.g., rifampicin, carbamazepine): reduce effectiveness, may lead to clotting.
• Vitamin K‑rich foods or supplements: can diminish anticoagulant effect, require INR monitoring.
• Herbal products (e.g., ginkgo, garlic): may increase bleeding risk, advise caution.