WARFARIN

Indications & Dose:

Prophylaxis of embolisation in rheumatic heart disease and atrial fibrillation Prophylaxis after insertion of prosthetic heart valve

Prophylaxis and treatment of venous thrombosis and pulmonary embolism

Transient ischaemic attacks

• BY MOUTH

Adult: Initially 5–10 mg, to be taken on day 1; subsequent doses dependent on the prothrombin time, reported as INR (international normalised ratio), a lower induction dose can be given over 3–4 weeks in patients who do not require rapid anticoagulation, elderly patients to be given a lower induction dose; maintenance 3–9 mg daily, to be taken at the same time each day

Contraindications:

Active bleeding, hemorrhagic blood dyscrasias; hemorrhagic tendencies, history of bleeding diathesis, recent cerebral hemorrhage; active ulceration of the GI tract; ulcerative colitis; open traumatic or surgical wounds; recent or contemplated brain, eye, spinal cord surgery, or prostatectomy; regional or lumbar block anesthesia; bacterial endocarditis; pericarditis; visceral carcinoma; severe or malignant hypertension; eclampsia or preeclampsia; threatened abortion; emaciation; prey; history of warfar in induced skin necrosis; uncooperative, patient

Side Effects:

GI: Anorexia, cholestatic jaundice, hepatotoxicity, mouth ulcers, nausea, paralytic ileus, sore mouth, vomiting

GU: Albuminuria, anuria, red-orange urine, renal tubular necrosis

HEME: Hemorrhage, leukopenia

SKIN: Alopecia, dermatitis, exfoliative dermatitis, necrosis or gangrene of skin and other tissues, urticaria

MISC: Systemic cholesterol microembolization (“purple toe” syndrome)

Cautions:

Precautions:

Trauma,infection,renalinsufficiency, hypertension, vasculitis, indwellingcatheters, severe diabetes; active tuberculosis,postpartum,  protein  C  deficiency,  hepaticinsufficiency, elderly, children, hyperthyroidism,hypothyroidism, CHF, polyarteritis, diverticulitis,antibiotic therapy, malnutrition

PREGNANCY ; use in 1st trimester carries significant risk to the fetus; exposure in the 6th-9thwk of gestation may produce a pattern of defects termed the fetal warfarin syndrome with an incidence up to 25%a in some series; compatible with breast feeding for normal, full-term infants

Interaction:

Drugs 

Acetaminophen: Repeated doses of acetaminophen may increase the hypoprothrombinemic response to warfarin

Allopurinol, amiodarone, ciprofloxacin, clarithromycin, erythromycin, fluconazole, fluorouracil, fluvastatin, fluvoxamine, glucagon, isoniazid, itraconazole, ketoconazole, lovastatin. miconazole, nalidixic acid, neonrvvin (oral), norfloxacin, ofloxacin. propafenone, propoxyphene, quinidine, sertraline, sulfonamides, sulfonylureas, thyroid hormones, triclofos, troleandomycin, vitamin E, zafirlukast: Enhanced hypoprothrombinemic response to warfarin

Aminoglutethimide, carbamazepine, cyclophosphamide, ethchlorvynol, griseofulvin, mercaptopurine, methimazole, mitotane, nafcillin, propylthiouracil, vitamin K: Reduced hypoprothrombinemic response to warfarin.

Aspirin: Increased risk of bleeding complications

Azathioprine, chloramphenicol, cimetidine, clofibrate,co-trimoxazole,danazole,dextrothyroxine, disulfiram, gemfibrozil, metronidazole, sulfinpyrazone, testosterone derivatives: Enhanced hypoprothrombinemic response to warfarin

Barbiturates, glutethimide, rifampin: Reduced hypoprothrombinemic response to warfarin

Bile acid-binding resins: Variable effect on hypoprothrombinemic effect of warfarin

Cephalosporins: Enhanced hypoprothrombinemic response to warfarin with moxalaotam, cefoperazone, cefunandole, cefotetan, andcefrnetazole

Chloral hydrate: Transient increase in hypoprothrombinemic response to warfarin

Ethanol: Enhanced hypoprothrombinemic response to warfarin with acute ethanol intoxication

Heparin: Prolonged activated partial thromboplastin time in patients receiving heparin; prolonged prothrombin times in patients receiving warfarin

Mesalamine: Warfarin effect inhibited in one case report

NSAIDs: Increased risk of bleeding in anticoagulated patients

Oral contraceptives: Increase or decrease in anticoagulant response; increased risk of thromboembolic disorders

Phenytoin: Transient increase in hyprothrombinemic, response to warfarin with initiation of phenytoin therapy, followed within 1-2 wk by inhibition of hypoprothrombinemic response to warfarin

Salicylates:  Increased  risk  of  bleeding in anticoagulated patients; enhanced hypoprothrombinemic response to warfarin with large salicylate doses

Warnings:

Adverse Effects:

Lactations:

Special Precautions:

Counselling:

Side Effects Or Adverse Reactions:

Patient And Carer Advice: