Warfarin inhibits vitamin K dependent coagulation factors. It is used to thin the blood in patients who have had deep vein thrombosis (DVT) or pulmonary embolism or have a high risk of forming blood clots in the heart secondary to atrial fibrillation or mechanical heart valve replacement. Almost all overdoses occur because of errors in dosing and/or drug-drug interactions. The overdose may cause no symptoms and only be recognized on a blood test that demonstrates a high Prothrombin Time (PT) or high INR (International Normalized Ratio). However, overdoses can lead to life threatening bleeding.
Description
Warfarin inhibits vitamin K dependent coagulation factors. It is used to thin the blood in patients who have had deep vein thrombosis (DVT) or pulmonary embolism or have a high risk of forming blood clots in the heart secondary to atrial fibrillation or mechanical heart valve replacement. Almost all overdoses occur because of errors in dosing and/or drug-drug interactions. The overdose may cause no symptoms and only be recognized on a blood test that demonstrates a high Prothrombin Time (PT) or high INR (International Normalized Ratio). However, overdoses can lead to life threatening bleeding.
Symptoms
Excess bleeding can occur anywhere in the body, including: nosebleeds, bleeding gums, vomiting blood, vomiting coffee ground material, bloody stools, black stools (melena), bleeding in and around the brain.
Tests
Common tests used for diagnosis and treatment
Workup:
A history and physical exam will be performed. A high PT/INR makes the diagnosis of an overdose of warfarin.
Tests:
Pregnancy (BHCG) test, Complete blood count (CBC), Comprehensive metabolic panel (CMP), CT Scan
Other Specific Tests: PT (Protime)
Specialists:
Blood and Cancer Care (hematology and oncology), Pediatric Hematology and Oncology, Medical Toxicology
Workup:
A history and physical exam will be performed. A high PT/INR makes the diagnosis of an overdose of warfarin.
Tests:
Pregnancy (BHCG) test, Complete blood count (CBC), Comprehensive metabolic panel (CMP), CT Scan
Other Specific Tests: PT (Protime)
Specialists:
Blood and Cancer Care (hematology and oncology), Pediatric Hematology and Oncology, Medical Toxicology
Treatment
Warfarin is immediately discontinued. A slightly elevated INR is treated by not taking warfarin for one or two days and restarting at a lower dose. Higher INRs without symptoms are treated with low dose oral vitamin K. Very high INR levels and/or active bleeding are usually treated with intravenous vitamin K. Patients with bleeding may also need intravenous fluids, red blood cell transfusions, fresh frozen plasma and/or factor IX concentrate administration.