Warfarin (Coumadin)

Drug Class

Anticoagulant

Side effects

Anorexia, nausea, vomiting, diarrhea, abdominal cramps, rash, alopecia, fever, stomatitis

Contraindications

Bleeding Disorder, peptic ulcer, cerebrovascular accident, severe hepatic or renal disease, hemophilia, eclampsia, alcoholism, head trauma Caution: diabetes mellitus, leukemia

Mode of action

Depresses hepatic synthesis of vitamin K clotting factores (II [prothrombin], VII, IX and X)

Drug-Lab-Food interactions

Drug: increase effect with amiodarone, aspirin, NSAIDs, sulfonamides, thyroid drugs, allopurinol, histamine2 blockers, oral hypoglycemic, metronidazole, miconazole, methyldopa, diuretics, oral antibiotics, vitamin E; decrease effect with barbiturates, laxatives, phenytoin, estrogen, vitamins C and K, oral contraceptives, rifampin Lab: May increase AST, ALT Food: Decrease diet rich in vitamin K

Evaluation

Evaluate effectiveness of drug therapy. Patient's PT or INR values are within desired range, and patient is free from significant side effects.

Patient Teaching

General: Teach patient to inform dentist when taking. Advise patient to use soft toothbrush to prevent gums from bleeding. Warn patient to shave with an electric razor. Bleeding from shaving cuts may be difficult to control. Advise patient to have lab tests such as PT or INR performed as ordered. Encourage patient not to smoke. Smoking increases drug metabolism, so warfarin dose may need to be increased. Tell the patient to check with health care provider before taking OTC drugs. Suggest that patient use acetaminophen instead of aspirin (aspirin should NOT be taken with warfarin) Inform patient that may herbal products interact and may increase bleeding (Dong quai, feverfew, garlic, ginger, green tea, ginko, bilberry etc.) Teach patient to control external hemorrhage from accidents or injuries by applyingfirm, direct pressure for at least 5-10 mins with a clean dry, absorbent material. Side effects: Warn patient to report frank or occult bleeding (petechiae, ecchymosis, purpura, tarry stools, bleeding gums, epistaxis, expectoration of blood) Diet: Advise patient to avoid large amounts of green leafy vegetables; broccoli; legumes; soy bean oil (rich in Vitamin K); coffee, tea, cola (Caffeine); excessive alcohol; and certain herbs and nutritional supplements (coenzyme Q10) or to be very consistent with their intake Coenzyme Q10, fish oils, items high in vitamin K, St. John's Wort, ginseng, and vitamin C may decrease effectiveness of warfarin along with garlic, ginger, kava kava, green tea, chamomile tea, ginkgo biloba, and acute alcohol intoxication.

Life threatening and other adverse reactions

Life Threatening: Hemorrhage Other: Purple toe syndrome

Nursing interventions

Monitor vital signs. An increased pulse rate followed by a decreased systolic pressure can indicate a fluid volume deficit resulting from external or internal bleeding Examine patient's mouth, nose (epistaxis), urine (hematuria), and skin (purpura, petechiae) for bleeding. Watch older adults closely for bleeding; their skin is thin, and capillary beds are fragile. Check stools periodically for occult blood. Keep anticoagulant antagonists (Vit K) available when drug dose is increased or there are indications of frank bleeding. Fresh-frozen plasma may be needed for transfusion.

Assessment

Obtain a history of abnormal clotting or health problems that affect clotting, such as severe alcoholism or severe liver or renal disease. Report if drug-drug or drug-herbal interaction is probable. Warfarin is highly protein bound and can displace other highly bound protein bound drugs, or warfarin could be displaced, which may result in bleeding. Develop a flowchart that lists prothrombin time (PT) or international normalized ratio (INR) and warfarin dosages. A baseline PT or INR should be obtained before warfarin is administered.

Route of admin

PO

Planning

Patient's PT will be 1.25 to 2.5 times control level, or INR will be 2-3. Patient will not have excessive bleeding

True or False: Warfarin has a long half life and a very long duration.

True

Uses

Used to prevent thromboembolic conditions such as thrombophlebitis, pulmonary embolism, and embolism formation caused by atrial fibrillation, which can lead to stroke (CVA).

The antidote for warfarin overdose is vitamin K, but....?

it takes 24-48 hours to be effective.