Coumadin Special Precautions

Periodic determination of PT or other suitable coagulation test is essential.
Numerous factors, alone or in combination, including travel, changes in diet, environment, physical state and medication may influence response of the patient to anticoagulants. It is generally good practice to monitor the patient's response with additional PT determinations in the period immediately after discharge from the hospital, and whenever other medications are initiated, discontinued or taken haphazardly. The following factors are listed for reference; however, other factors may also affect the anticoagulant response.
The following factors, alone or in combination, may be responsible for increased PT response: Endogenous Factors: Cancer; collagen disease; congestive heart failure; diarrhea; elevated temperature; hepatic disorders (infectious hepatitis, jaundice); hyperthyroidism; poor nutritional state; steatorrhea and vitamin K deficiency.
Exogenous Factors: Acetaminophen, alcohol*; allopurinol; aminosalicylic acid; amiodarone HCl; anabolic steroids; anesthetics (inhalation), antibiotics; bromelains; chenodiol, chloral hydrate*; chlorpropamide; chymotrypsin; cimetidine; clofibrate; Coumadin overdosage; dextran; dextrothyroxine; diazoxide; diflunisal; diuretics*; disulfiram; ethacrynic acid; fenoprofen; fluoroquinolone antibiotics, glucagon; hepatotoxic drugs; ibuprofen, indomethacin; influenza virus vaccine; lovastatin, mefenamic acid; methyldopa; methylphenidate; metronidazole, miconazole; MAOIs; moricizine HCl*; nalidixic acid; naproxen; pentoxifylline; phenylbutazone; phenytoin; prolonged narcotics; propafenone, pyrazolones, quinidine, quinine; ranitidine*; salicylates; sulfinpyrazone; long-acting sulfonamides; sulindac; tamoxifen, thyroid drugs; tolbutamide; trimethoprim/sulfamethoxazole; also, other medications affecting blood elements which may modify hemostasis; dietary deficiencies; prolonged hot weather, unreliable PT determinations.
*Increased and decreased PT responses have been reported.
The following factors, alone or in combination, may be responsible for decreased PT response: Endogenous Factors: Edema; hereditary coumarin resistance; hyperlipemia; hypothyroidism.
Exogenous Factors: Adrenocortical steroids; alcohol*; aminoglutethimide, antacids; antihistamines; barbiturates; carbamazepine; chloral hydrate*; chlordiazepoxide; cholestyramine; Coumadin underdosage; diuretics*; ethchlorvynol; glutethimide; griseofulvin; haloperidol; meprobamate; moricizine HCl*, nafcillin, oral contraceptives; paraldehyde; primidone; ranitidine*; rifampin; sucralfate, trazodone, vitamin C; also, diet high in vitamin K; unreliable PT determinations.
*Increased and decreased PT responses have been reported.
Because a patient may be exposed to a combination of the previously mentioned factors, the net effect of Coumadin on PT response may be unpredictable. More frequent PT monitoring is therefore advisable.
Medications of unknown interaction with coumarins are best regarded with caution when these medications are started or stopped, more frequent PT monitoring is advisable.
Coumarins may also affect the action of other drugs. Hypoglycemic agents (chlorpropamide and tolbutamide) and anticonvulsants (phenytoin and phenobarbital) may accumulate in the body as a result of interference with either their metabolism or excretion.
It has been reported that concomitant administration of warfarin and ticlopidine may be associated with cholestatic hepatitis.
Special Risk Patients: Caution should be observed when warfarin sodium is administered to certain patients eg, the elderly or debilitated or when administered in any situation or physical condition where added risk of hemorrhage is present.
Intramuscular (IM) injections of concomitant medications should be confined to the upper extremities which permits easy access for manual compression, inspections for bleeding and use of pressure bandages.
Caution should be observed when Coumadin (or warfarin) is administered concomitantly with nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, to be certain that no change in anticoagulation dosage is required. In addition to specific drug interactions that might affect PT, NSAIDs, including aspirin, can inhibit platelet aggregation and can cause gastrointestinal bleeding, peptic ulceration and/or perforation.
Information for Patients: The objective of anticoagulant therapy is to control the coagulation mechanism so that thrombosis is prevented while avoiding spontaneous bleeding. Effective therapeutic levels with minimal complications are in part dependent upon cooperative and well-instructed patients who communicate effectively with their physician. Various Coumadin patient educational guides are available to physicians on request.
Patients should be advised: Strict adherence to prescribed dosage schedule is necessary. Do not take or discontinue any other medication, except on advice of physician. Avoid alcohol, salicylates (eg, aspirin and topical analgesics), large amounts of green leafy vegetables and/or drastic changes in dietary habits, which may affect Coumadin therapy. Coumadin may cause a red-orange discoloration of alkaline urine. The patient should notify the physician if any illness eg, diarrhea, infection or fever develops or if any unusual symptoms eg, pain, swelling or discomfort appear or if prolonged bleeding from cuts, increased menstrual flow or vaginal bleeding, nosebleeds or bleeding of gums from brushing, unusual bleeding or bruising, red or dark brown urine, red or tar black stools or diarrhea occurs.
Carcinogenicity, Mutagenicity & Impairment of Fertility: Carcinogenicity and mutagenicity studies have not been performed with Coumadin. The reproductive effects of Coumadin have not been evaluated.
Use in pregnancy: Pregnancy Category X: See Contraindications.
Use in children: Safety and effectiveness in children <18 years have not been established.