Substance
Warfarin and related anticoagulant compounds

Pathology
Inhibition of vitamin K 2,3-epoxide reductase and quinone reductase activity (these are necessary to activate vitamin K, which is essential in coagulation).

Symptoms
Fatigue, hematuria, nosebleeds, ecchymoses, GI hemorrhage, hypotension, intracranial hemorrhage, hemorrhagic shock, death (rare).

Emergency Measures
Decontaminate the GI tract (for recent ingestions only). Hold warfarin if the protime is slightly elevated and no bleeding is present. Give vitamin K for markedly prolonged protimes with INR greater than 6–9 or fresh frozen plasma for life-threatening bleeding.

Comments
Most accidental ingestions resolve without further sequelae. Intentional ingestions or delay in seeking treatment may result in severe coagulopathy. Bleeding patients require hospitalization, frequent monitoring of blood pressure, pulse, and hemoglobin levels. Cauterization of bleeding lesions may be needed.