The mechanism was thought to be a combination of reduced intake of vitamin K (a vitamin necessary for bone health) and inhibition by warfarin of vitamin K-mediated carboxylation of certain bone proteins, rendering them nonfunctional. Purple toe syndrome
Another rare complication that may occur early during warfarin treatment (usually within 3 to 8 weeks of commencement) is purple toe syndrome. This condition is thought to result from small deposits of cholesterol breaking loose and causing embolisms in blood vessels in the skin of the feet, which causes a blueish-purple colour and may be painful.It is typically thought to affect the big toe, but it affects other parts of the feet, as well, including the bottom of the foot (plantar surface). The occurrence of purple toe syndrome may require discontinuation of warfarin. Calcification
Several studies have also implicated warfarin use in valvular and vascular calcification. No specific treatment is available, but some modalities are under investigation. Overdose
The major side effect of warfarin use is bleeding. Risk of bleeding is increased if the INR is out of range (due to accidental or deliberate overdose or due to interactions). Many drug interactions can increase the effect of warfarin, also causing an overdose.In patients with supratherapeutic INR but INR less than 10 and no bleeding, it is enough to lower the dose or omit a dose, monitor the INR and resume warfarin at an adjusted lower dose when the target INR is reached.
Historical information on warfarin from the Wisconsin Alumni Research Foundation
CDC – NIOSH Pocket Guide to Chemical Hazards
Warfarin in the Pesticide Properties DataBase (PPDB)