Warfarin (Coumadin) Toxicity: Be Careful

Warfarin (Coumadin), a vitamin K antagonist, is the most commonly prescribed oral anticoagulant medication in use today. This drug is widely used because it is beneficial in the treatment of numerous medical problems, including chronic atrial fibrillation, mechanical heart valves, deep venous thrombosis, pulmonary embolism, antiphospholipid syndrome, myocardial infarction (heart attack), cerebrovascular accident (stroke), dilated cardiomyopathy, and other conditions. Warfarin aids in preventing future blood clots and lessens the likelihood of embolism because it maintains anticoagulation in places where blood tends to pool or move slowly.

Even though many people refer to warfarin as a 'blood thinner,' this label is not accurate because it does nothing to alter the blood's viscosity. According to the Occupational Safety and Health Administration (n.d.), warfarin acts on the liver to inhibit prothrombin formation, which interferes with blood clotting. Warfarin inhibits vitamin K–dependent clotting factors II, VII, IX, and X and the anticoagulant proteins C and S (Russell, 2011). Since this medication has a very narrow therapeutic range, patients who take warfarin need frequent monitoring of laboratory values.

Bleeding is the cardinal sign of warfarin toxicity, and too much of this drug may result in potentially fatal hemorrhage. According to the Occupational Safety and Health Administration (n.d.), the signs and symptoms of acute exposure (i.e., for a period of one week or less) to warfarin include bloody nose; bleeding gums; muscle and joint pain; hematomas of the arms, legs, buttocks, and/or joints; frank blood in the urine and feces; anorexia, nausea, vomiting, diarrhea or abdominal pain; pallor and fatigue caused by anemia; paralysis caused by intracranial hemorrhage; blurry vision, eye pain, and blindness; and/or skin lesions and petechiae. Warfarin may result in necrosis or gangrene. The signs and symptoms of chronic warfarin toxicity are the same as the ones listed above.

Nurses, physicians, and pharmacists must provide education on the signs and symptoms of warfarin toxicity to patients and their family members. Provide patients with a list of foods that are especially rich in vitamin K, and instruct them to avoid consuming these food items. This medication should be taken at the same time every day. Patients must inform all other healthcare providers that they are taking warfarin, especially if they will undergo a dental or surgical procedure. Since warfarin is teratogenic (harmful to the fetus), female patients must be directed to tell their doctor if they are pregnant or planning to become pregnant. Instruct patients to consult with their physician prior to taking herbal products or nutritional supplements.

Since anticoagulation therapy is so widely used in healthcare settings, it is imperative that nurses and other healthcare workers are knowledgeable about the action of warfarin. Knowledge is power, and together we can bestow education upon our patients and their families to assist in preventing deadly complications.