Warfarin Drug Study

In making a Drug Study, the following elements must be present: Generic Name and the Brand name (not all brands, just the brand used by the patient), Action, Indication, Pregnancy Category, Drug Classification, and Contraindication, Adverse Effect, Drug interaction and Nursing Consideration/Intervention…. Most clinical instructors preferred this to be in a long bond paper in printed or handwritten with paper in landscape.

Warfarin sodium

Brand Name: Coumadin, Warfilone (CAN)

Pregnancy Category X

Drug classes: Oral anticoagulant, Coumarin derivative

Therapeutic actions

Interferes with the hepatic synthesis of vitamin K-dependent clotting factors (factors II-prothrombin, VII, IX, and X), resulting in their eventual depletion and prolongation of clotting times.

Indications

· Venous thrombosis and its extension, treatment, and prophylaxis

· Treatment of thromboembolic complications of atrial fibrillation with embolization, and cardiac valve replacement

· Pulmonary embolism, treatment, and prophylaxis

· Prophylaxis of systemic embolization after acute MI

· Unlabeld uses: prevention of recurrent TIAs, prevention of recurrent MI, adjunct to therapy in small-cell carcinoma of the lung

Contraindications

· Contraindicated with allergy to warfarin; SBE; hemorrhagic disorders; TB; hepatic diseases; GI ulcers; renal disease; indwelling catheters, spinal puncture; aneurysm; diabetes; visceral carcinoma; uncontrolled hypertension; severe trauma (including recent or contemplated CNS, eye surgery; recent placement of IUD); threatened abortion, menometrorrhagia; pregnancy (fetal damage and death); lactation (suggest using heparin if anticoagulation is required).

Adverse effects

Hemorrhage; GI or urinary tract bleeding (hematuria, dark stools; paralytic ileus, intestinal obstruction from hemorrhage into GI tract); petechiae and purpura, bleeding from mucous membranes; hemorrhagic infarction, vasculitis, skin necrosis of female breast; adrenal hemorrhage and resultant adrenal insufficiency; compressive neuropathy secondary to hemorrhage near a nerve, Alopecia, urticaria, dermatitis, Nausea, vomiting, anorexia, abdominal cramping, diarrhea, retroperitoneal hematoma, hepatitis, jaundice, mouth ulcers, Priapism, nephropathy, red-orange urine, Granulocytosis, leukopenia, eosinophilia, Fever, "purple toes" syndrome

Drug Interactions:

· Increased bleeding tendencies with salicylates, chloral hydrate, phenylbutazone, clofibrate, disulfiram, chloramphenicol, metronidazole, cimetidine, ranitidine, co-trimoxazole, sulfinpyrazone, quinidine, quinine, oxyphenbutazone, thyroid drugs, glucagon, danazol, erythromycin, androgens, amiodarone, cefamandole, cefoperazone, cefotetan, moxalactam, cefazolin, cefoxitin, ceftriaxone, meclofenamate, mefenamic acid, famotidine, nizatidine, nalidixic acid

· Decreased anticoagulation effect may occur with barbiturates, griseofulvin, rifampin, phenytoin, glutethimide, carbamazepine, vitamin K, vitamin E, cholestyramine, aminoglutethimide, ethchlorvynol

· Altered effects with methimazole, propylthiouracil

· Increased activity and toxicity of phenytoin when taken with oral anticoagulants

Nursing considerations

· Do not use drug if patient is pregnant (heparin is anticoagulant of choice); advise patient to use contraceptives.

· Monitor PT ratio or INR regularly to adjust dosage.

· Administer IV form to patients stabilized on Coumadin who are not able to take oral drug. Dosages are the same. Return to oral form as soon as feasible.

· Do not change brand names once stabilized; bioavailability problems exist.

· Evaluate patient regularly for signs of blood loss (petechiae, bleeding gums, bruises, dark stools, dark urine). Maintain PT ratio of 1.3–1.5, 1.5–2 with mechanical prosthetic valves or recurrent systemic embolism; INR ratio of 2–3, 3–4.5 with mechanical prosthetic valves or recurrent systemic emboli.

· Do not give patient any IM injections.

· Double check all drugs ordered for potential drug–drug interaction; dosage of both drugs may need to be adjusted.

· Use caution when discontinuing other medications; warfarin dosage may need to be adjusted; carefully monitor PT values.

· Maintain vitamin K on standby in case of overdose.

· Arrange for frequent follow-up, including blood tests to evaluate drug effects.

· Evaluate for therapeutic effects: PT 1.5–2.5 times the control value; PT ratio, INR within therapeutic range.