Phenprocoumon is an anticoagulant medication used to prevent blood clots in patients at risk for conditions such as deep vein thrombosis or pulmonary embolism. It works by inhibiting the synthesis of vitamin K-dependent clotting factors in the liver, which helps to reduce the blood's ability to clot. This medication is often prescribed for long-term use, especially in patients with atrial fibrillation or those who have undergone certain surgeries. Regular monitoring of blood coagulation levels is necessary to ensure the correct dosage and minimize the risk of bleeding complications.