Marcoumar (Phenprocoumon)

Phenprocoumon is used to manage conditions that involve abnormal blood clot formation.

• Deep‑vein thrombosis: prevents clot extension and recurrence in patients with DVT.
• Pulmonary embolism: treats and reduces the risk of recurrent embolic events.
• Atrial fibrillation (stroke prevention): lowers the incidence of ischemic stroke in non‑valvular AF.
• Prosthetic heart valves: provides long‑term anticoagulation to avoid valve‑related thrombosis.

• Phenprocoumon inhibits vitamin K epoxide reductase, an enzyme required to recycle vitamin K to its active form. By blocking this step, the synthesis of vitamin K‑dependent clotting factors II, VII, IX and X is reduced, leading to diminished thrombin generation and prolonged coagulation time, which helps prevent pathological clot formation.

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

Common Side Effects

• Bruising or easy bruising.
• Bleeding gums or nosebleeds.
• Gastrointestinal discomfort or dyspepsia.
• Headache or dizziness.
• Skin rash or mild itching.
• Minor hematuria.

Serious or Rare Side Effects

• Severe internal bleeding (e.g., intracranial or gastrointestinal).
• Skin necrosis or severe cutaneous reactions.
• Hepatic enzyme elevation or liver dysfunction.
• Allergic anaphylaxis.
• Thrombocytopenia.
• Adrenal insufficiency or other endocrine disturbances.

Patients receiving Phenprocoumon should be monitored closely for safety and efficacy.

• INR monitoring: maintain therapeutic range as directed by a healthcare professional.
• Liver disease: adjust dose or avoid use in significant hepatic impairment.
• Surgery or invasive procedures: discontinue or bridge therapy according to clinical guidance.
• Elderly patients: start with lower doses and monitor for bleeding.
• Pregnancy: contraindicated; avoid use in pregnant women (Category X).
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Other anticoagulants (e.g., heparin, direct oral anticoagulants): markedly increased bleeding risk.
• Strong CYP2C9 inhibitors (e.g., amiodarone, fluconazole, metronidazole): may cause excessive anticoagulation.
• Antiplatelet agents (e.g., aspirin, clopidogrel): additive bleeding potential.

Moderate Interactions (Monitor Closely)

• Certain antibiotics (e.g., macrolides, quinolones): may modestly increase INR.
• SSRIs or SNRIs: can enhance bleeding tendency.
• Vitamin K–containing supplements or foods: may reduce anticoagulant effect.
• Thyroid hormones: may alter drug metabolism and INR stability.