warfarin, Coumadin, Jantoven (cont.)

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Drugs that may reduce the effect of warfarin by increasing its breakdown include St. John's wort, carbamazepine (Tegretol, Tegretol XR, Equetro, Carbatrol), rifampin, bosentan (Tracleer), and prednisone.

Bleeding is increased by other anticoagulants such as heparin, argatroban (Acova), dabigatran (Pradaxa), and others; antiplatelet drugs such as aspirin and other nonsteroidal anti-inflammatory drugs (for example, ibuprofen [Motrin], naproxen [Alleve]), clopidogrel (Plavix), and prasugrel (Effient); serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) and paroxetine (Paxil). Garlic and ginkgo also increase the risk of bleeding because they cause bleeding when taken alone.

Foods with high vitamin K content (for example, green leafy vegetables) reduce the effect of warfarin. Maintenance of a consistent intake of vitamin K containing foods is important to avoid fluctuations in the effect of warfarin.

PREGNANCY: Warfarin should be avoided by pregnant women or women who may become pregnant. Birth defects and fetal bleeding have been reported.

NURSING MOTHERS: Available evidence suggests that warfarin is not secreted in breast milk.

SIDE EFFECTS: The two most serious side effects of warfarin are bleeding and necrosis (gangrene) of the skin. Bleeding can occur in any organ or tissue. Bleeding around the brain can cause severe headache and paralysis. Bleeding in the joints can cause joint pain and swelling. Bleeding in the stomach or intestines can cause weakness, fainting spells, black tarry stools, vomiting of blood, or coffee ground material. Bleeding in the kidneys can cause back pain and blood in urine. Other side effects include purple, painful toes, rash, hair loss, bloating, diarrhea, and jaundice (yellowing of eyes and skin). Signs of overdose include bleeding gums, bruising, nosebleeds, heavy menstrual bleeding, and prolonged bleeding from cuts.

Reference: FDA Prescribing Information

Last Editorial Review: 1/4/2013

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