From Wiki-P:

Purple toe syndrome
Another rare complication that may occur early during warfarin treatment (usually within 3 to 8 weeks) is purple toe syndrome. This condition is thought to result from small deposits of cholesterol breaking loose and flowing into the blood vessels in the skin of the feet, which causes a blueish purple color 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.[22]

Self-testing and home monitoring
Patients are making increasing use of self-testing and home monitoring of oral anticoagulation. International guidelines were published in 2005 to govern home testing, by the International Self-Monitoring Association for Oral Anticoagulation.[2]

The international guidelines study stated: "The consensus agrees that patient self-testing and patient self-management are effective methods of monitoring oral anticoagulation therapy, providing outcomes at least as good as, and possibly better than, those achieved with an anticoagulation clinic. All patients must be appropriately selected and trained. Currently-available self-testing/self-management devices give INR results that are comparable with those obtained in laboratory testing."[2]


[edit] Interactions
Warfarin interacts with many commonly-used drugs, and the metabolism of warfarin varies greatly between patients. Some foods have also been reported to interact with warfarin.[1] Apart from the metabolic interactions, highly protein bound drugs can displace warfarin from albumin and cause an increase in INR.[37] This makes finding the correct dosage difficult, and accentuates the need of monitoring; when initiating a medication that is known to interact with warfarin (e.g. simvastatin), INR checks are increased or dosages adjusted until a new ideal dosage is found.

Many commonly-used antibiotics, such as metronidazole or the macrolides, will greatly increase the effect of warfarin by reducing the metabolism of warfarin in the body. Other broad-spectrum antibiotics can reduce the amount of the normal bacterial flora in the bowel, which make significant quantities of vitamin K, thus potentiating the effect of warfarin.[38] In addition, food that contains large quantities of vitamin K will reduce the warfarin effect.[1] Thyroid activity also appears to influence warfarin dosing requirements;[39] hypothyroidism (decreased thyroid function) makes people less responsive to warfarin treatment,[40] while hyperthyroidism (overactive thyroid) boosts the anticoagulant effect.[41] Several mechanisms have been proposed for this effect, including changes in the rate of breakdown of clotting factors and changes in the metabolism of warfarin.[42][39]

Excessive use of alcohol is also known to affect the metabolism of warfarin and can elevate the INR.[43] Patients are often cautioned against the excessive use of alcohol while taking warfarin.

Warfarin also interacts with many herbs, including—but not limited to—the following:[44]

Ginkgo (a.k.a. Ginkgo Biloba), which is commonly used to increase brain blood flow, prevent dementia, and improve memory. However, ginkgo may increase blood pressure, and may increase bleeding, especially in people already taking certain anti-clotting medications such as warfarin.

St. John's Wort is commonly used to help with mild to moderate depression. However, it may prolong the effects of certain anesthetic drugs and reduce the effects oral contraceptives and anti-organ transplant rejection medications, and interfere with warfarin.

Ginseng is commonly used to help with fatigue and weakness. However, ginseng may increase blood pressure and heart rate and may increase bleeding, especially in people already taking certain anti-clotting medications such as warfarin.

Garlic (as a supplement, not in the diet) is commonly used to help lower high cholesterol levels, high triglycerides, and high blood pressure. However, may increase bleeding especially in people already taking certain anti-clotting medications such as warfarin.

Ginger is commonly used to help nausea and poor digestion. However, it may increase bleeding, especially in patients already taking certain anti-clotting medications such as warfarin.

Between 2003 and 2004, the UK Committee on Safety of Medicines received several reports of increased INR and risk of hemorrhage in people taking warfarin and cranberry juice.[45][46][47] Data establishing a causal relationship is still lacking, and a 2006 review found no cases of this interaction reported to the FDA;[47] nevertheless, several authors have recommended that both doctors and patients be made aware of its possibility.[48] The mechanism behind the interaction is still unclear.[47]

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