Lupus Site - a guide for lupus patients and their families

Brand names - Coumadin, Panwarfin, Sofarin, Marevan.

Medication type - Anticoagulant

Common side effects - No common side effects.

Rare side effects - Loss of appetite, unusual weight loss, nausea, vomiting, skin rash, diarrhea, cramping.

Serious side effects - Allergic reaction (marked by wheezing, breathing difficulty, hives, or swelling of lips, tongue, and throat); bleeding into skin and soft tissue; abnormal bleeding from nose, gastrointestinal tract, urinary tract, or uterus; severe infection; excessive or unexpected menstrual bleeding; black vomit; bruises or purple marks on skin. Consult your doctor immediately.

Dosage - Adults: To start, 10 to 15 mg daily, taken once a day. Long-term, usually 2 to 10 mg per day, taken once a day. Should be taken at the same time every day.

Uses - To prevent blood clot formation, by blocking the action of vitamin K, a compound necessary for blood clotting.

Food interactions - Avoid green, leafy vegetables and other foods that are rich in vitamin K (liver, broccoli, cauliflower, kale, spinach, and cabbage). Intake of too much vitamin K can override the anticlotting effect of warfarin and render the drug useless. Conversely, certain substances can interfere with the absorption of vitamin K so much that normal, healthy clotting (necessary for wounds to heal) is impaired. Megadoses of vitamin E can do this, as can fish oil supplements and foods high in omega-3 fatty acids. These substances can enhance the effect of anticlotting drugs so much that a tendency to haemorrhage may result.

Other notes - Regular tests of prothrombin time (a simple test that measures the time it takes for one stage of blood coagulation to occur) are needed when taking this drug. Your doctor may also take stool and urine samples periodically to check for the presence of blood. Use alcohol with caution, it can increase or decrease the effect of warfarin. Usually, consume no more than one drink a day. Warfarin may cause birth defects. Do not use during pregnancy. Warfarin passes into breast milk. Do not use while nursing.