Marcumar • Effects & side effects of the anticoagulant

The drug Marcumar contains the active ingredient phenprocoumon and inhibits blood clotting. It is used in certain cardiovascular diseases or after operations to prevent the formation of vascular occlusions. More about the effect, areas of application and side effects.

The drug Marcumar contains the active ingredient phenprocoumon, which is referred to as the “antagonist” of vitamin K (vitamin K antagonist). Vitamin K is required for the production of coagulation factors in the liver. Phenprocoumon displaces vitamin K from its site of action in the liver, causing fewer clotting factors to be produced and reducing the ability of the blood to clot. This prevents blood clots from forming.

Article content at a glance:

Vitamin K: foods that contain a lot

Areas of application: When is Marcumar used?

The drug Marcumar is always used when there is a risk of vascular occlusion:

  • for the prevention or treatment of thrombosis and embolism

  • after operations on blood vessels or heart valves

  • for long-term treatment of heart attack patients and atrial fibrillation (prevention of blood clots in the heart)

  • in case of prolonged immobility after hip or leg surgery

Contraindications of Marcumar

Under no circumstances should Marcumar be used in people with known hypersensitivity to the active ingredient phenprocoumon. Since Marcumar reduces blood clotting, the benefit should always be carefully weighed against the risk of bleeding.

The active ingredient phenprocoumon is not recommended in the following cases:

  • pathological tendency to bleed (haemorrhagic diathesis)

  • severe liver disease (hepatic parenchymal disease)

  • Severely restricted kidney function (chronic renal failure)

  • severe lack of blood platelets (thrombocytopenia)

Even if there is a suspicion of damage to the vascular system, Marcumar should not be used. This is the case, for example, with:

  • sudden stroke (apoplectic stroke)

  • Inflammation of the sac around the heart (pericarditis) or the lining of the heart (endocarditis)

  • Enlargement of an arterial vessel in the brain (cerebral artery aneurysm)

  • Widening of the main artery (dissecting aortic aneurysm)

  • Ulcers (ulcers) in the gastrointestinal tract

  • an operation on the eye

  • Retinal diseases (retinopathies) with a risk of bleeding

  • Injuries or surgical procedures to the central nervous system

  • Pulmonary tuberculosis with cavitation (cavernosal pulmonary tuberculosis)

  • urological operations as long as there is a tendency to bleed

  • extensive open wounds, also after surgical interventions

When taking Marcumar during pregnancy, there is an increased risk of complications such as bleeding, malformations and miscarriage. Therefore, the drug must not be taken during this time. Taking phenprocoumon should be carefully considered if you are breastfeeding or have a history of epilepsy, alcoholism or kidney stones.

Dosage of the anticoagulant Marcumar

Phenprocoumon requires a prescription and is taken in tablet form. Since patients react differently to the active ingredient, the dosage is determined individually and checked regularly. This is done using the so-called INR value (International Normalized Ratio), which records blood coagulation.

At the beginning of Marcumar therapy, the INR value is determined daily, later every three to four weeks. Patients who have to take Marcumar permanently can also carry out this check themselves – all that is required is a drop of blood from the fingertip and a suitable measuring device. By regularly checking the coagulation values ​​and adjusting the dosage accordingly, a healthy balance is established between protection against blood clots and the increased risk of bleeding due to the anticoagulant effect of the drug.

Marcumar pass for emergencies

At the beginning of the therapy, every Marcumar patient receives a so-called “Marcumar passport” in which the INR value and phenprocoumon dosage are entered. Those affected should always carry this passport with them so that they can act quickly and correctly in an emergency. Before planned operations (including at the dentist), the Marcumar should be discontinued and, if necessary, replaced with the blood thinner heparin.

Side Effects of Marcumar

The most common side effect of phenprocoumon is bleeding, such as from the gums or nose. Bruises after bumps or bruises also occur frequently. This is associated with reduced blood clotting and is no cause for concern.

However, if any of the following symptoms occur, a doctor’s office or hospital should be contacted immediately:


  • heavy bleeding lasting more than five minutes

  • reddish to black urine

  • pitch black stool

  • burning pain in the big toes with simultaneous discoloration (purple toe syndrome)

  • severe, sudden headache, disturbances of vision or consciousness

Warning signals in urine: what color, smell and turbidity reveal

Marcumar: Interactions with other drugs

If other drugs are taken at the same time, the anticoagulant effect of Marcumar may be increased or decreased. Boosting drugs include:

  • other anticoagulants
  • remedies for gout
  • Drugs for cardiac arrhythmias
  • pain and rheumatism medication
  • Means for cancer therapy
  • Schildrüsenhormone
  • antidepressants
  • cholesterol-lowering agents

The effect of phenprocoumon can be weakened by:

  • Drugs for autoimmune diseases
  • anti-convulsants
  • water tablets (diuretics)
  • tranquilizers
  • diabetes medication
  • sleeping pills
  • Preparations with vitamin K or St. John’s wort
Medicines and food: These dangerous interactions exist

Source: Lifeline | Das Gesundheitsportal by www.lifeline.de.

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