PRECAUTIONS
PRECAUTIONS), and long duration of warfarintherapy. Regular monitoring of INR should be performed on all treated patients. Those at high risk of bleeding may benefitfrom more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy. Patientsshould be instructed about prevention measures to minimize risk of bleeding and to report immediately to physicians signsand symptoms of bleeding (see PRECAUTIONS,
INFORMATION FOR PATIENTS
Information for Patients).
DESCRIPTION
INACTIVE INGREDIENT
inactive ingredients: anhydrous lactose, hypromellose 2208 (3cPs), magnesium stearate,and pregelatinized starch.The 1 mg also contains D&C red no. 6 barium lake.The 2 mg also contains FD&C blue no. 2 aluminum lake, and FD&C red no. 40 aluminum lake.The 2275 mg also contains D&C yellow no. 10 aluminum lake, and FD&C blue no. 1 aluminum lake.The 3 mg also contains FD&C blue no. 2 aluminum lake, FD&C red no. 40 aluminum lake, and FD&C yellow no. 6 aluminum lake.The 4 mg also contains FD&C blue no. 1 aluminum lake.The 5 mg also contains FD&C yellow no. 6 aluminum lake.The 6 mg also contains FD&C blue no. 1 aluminum lake, and FD&C yellow no. 6 aluminum lake.The 7275 mg also contains D&C yellow no. 10 aluminum lake, and FD&C yellow no. 6 aluminum lake.The 10 mg does not contain any dyes.
CLINICAL PHARMACOLOGY
CLINICAL PHARMACOLOGYWarfarin sodium and other coumarin anticoagulants act by inhibiting the synthesis of vitamin K dependent clotting factors, whichinclude Factors II, VII, IX and X, and the anticoagulant proteins C and S. Half-lives of these clotting factors are as follows: Factor II- 60 hours, VII - 4 to 6 hours, IX - 24 hours, and X - 48 to 72 hours. The half-lives of proteins C and S are approximately 8 hours and30 hours, respectively. The resultant in vivo effect is a sequential depression of Factor VII, Protein C, Factor IX, Protein S, and FactorX and II activities. Vitamin K is an essential cofactor for the post ribosomal synthesis of the vitamin K dependent clotting factors. Thevitamin promotes the biosynthesis of g-carboxyglutamic acid residues in the proteins which are essential for biological activity. page 2 of 24
MECHANISM OF ACTION
Mechanism of ActionWarfarin is thought to interfere with clotting factor synthesis by inhibition of the C1 subunit of the vitamin K epoxide reductase(VKORC1) enzyme complex, thereby reducing the regeneration of vitamin K1 epoxide. The degree of depression is dependent uponthe dosage administered and, in part, by the patient222s VKORC1 genotype. Therapeutic doses of warfarin decrease the total amount ofthe active form of each vitamin K dependent clotting factor made by the liver by approximately 30% to 50%.An anticoagulation effect generally occurs within 24 hours after drug administration. However, peak anticoagulant effect may bedelayed 72 to 96 hours. The duration of action of a single dose of racemic warfarin is 2 to 5 days. The effects of warfarin sodiummay become more pronounced as effects of daily maintenance doses overlap. Anticoagulants have no direct effect on an establishedthrombus, nor do they reverse ischemic tissue damage. However, once a thrombus has occurred, the goal of anticoagulant treatment isto prevent further extension of the formed clot and prevent secondary thromboembolic complications which may result in serious andpossibly fatal sequelae.
PHARMACOKINETICS
PharmacokineticsWarfarin sodium is a racemic mixture of the R- and S-enantiomers. The S-enantiomer exhibits 2 to 5 times more anticoagulant activitythan the R-enantiomer in humans, but generally has a more rapid clearance.AbsorptionWarfarin sodium is essentially completely absorbed after oral administration with peak concentration generally attained within thefirst 4 hours.DistributionThere are no differences in the apparent volumes of distribution after intravenous and oral administration of single doses of warfarinsolution. Warfarin distributes into a relatively small apparent volume of distribution of about 0.14 liter/kg. A distribution phase lasting6 to 12 hours is distinguishable after rapid intravenous or oral administration of an aqueous solution. Using a one compartment model,and assuming complete bioavailability, estimates of the volumes of distribution of R- and S-warfarin are similar to each other and tothat of the racemate. Concentrations in fetal plasma approach the maternal values, but warfarin has not been found in human milk (see
WARNINGS
CLINICAL STUDIES
CONTRAINDICATIONS
CONTRAINDICATIONSAnticoagulation is contraindicated in any localized or general physical condition or personal circumstance in which the hazard ofhemorrhage might be greater than the potential clinical benefits of anticoagulation, such as:
PREGNANCY
ADVERSE REACTIONS
DRUG INTERACTIONS
drug interactions with warfarin sodium are synergism (impaired hemostasis, reduced clotting factorsynthesis), competitive antagonism (vitamin K), and altered physiologic control loop for vitamin K metabolism (hereditaryresistance). Pharmacokinetic mechanisms for drug interactions with warfarin sodium are mainly enzyme induction, enzymeinhibition, and reduced plasma protein binding. It is important to note that some drugs may interact by more than onemechanism.The following factors, alone or in combination, may be responsible for INCREASED PT/INR response:Endogenous Factors: blood dyscrasias-see CONTRAINDICATIONS hepatic disorders: infectious hepatitis cancer jaundice collagen vascular disease hyperthyroidism congestive heart failure poor nutritional state diarrhea steatorrhea elevated temperature vitamin K deficiency Exogenous Factors:Potential drug interactions with warfarin sodium are listed below by drug class and by specific drugs.Classes of Drugs 5-lipoxygenase Inhibitor Antiplatelet Drugs/Effects Leukotriene Receptor Antagonist Adrenergic Stimulants, Central Antithyroid Drugs* Monoamine Oxidase Inhibitors Alcohol
ABUSE
OVERDOSAGE
overdosage may result. A Medication Guide14 shouldbe available to patients when their prescriptions for warfarin sodium are issued.Carcinogenesis, Mutagenesis, Impairment of FertilityCarcinogenicity and mutagenicity studies have not been performed with warfarin sodium. The reproductive effects of warfarin sodiumhave not been eva luated. The use of warfarin during pregnancy has been associated with the development of fetal malformations inhumans (see CONTRAINDICATIONS).Use in PregnancyPregnancy Category X: See CONTRAINDICATIONS.
PEDIATRIC USE
Pediatric UseSafety and effectiveness in pediatric patients below the age of 18 have not been established in randomized, controlled clinical trials.However, the use of warfarin sodium in pediatric patients is well-documented for the prevention and treatment of thromboembolicevents. Difficulty achieving and maintaining therapeutic PT/INR ranges in the pediatric patient has been reported. More frequent PT/INR determinations are recommended because of possible changing warfarin requirements.
GERIATRIC USE
HOW SUPPLIED
HOW SUPPLIEDWarfarin Sodium Tablets, USP are available as: 1 mg: Pink, oval, scored tablet. Debossed with 831/1 on the scored side and stylized barr on theother side. Available in Bottles of: 100 Tablets NDC 0555-0831-02 1000 Tablets NDC 0555-0831-05 2 mg: Lavender, oval, scored tablet. Debossed with 869/2 on the scored and stylized barr on theother side. page 16 of 24 Available in Bottles of: 100 Tablets NDC 0555-0869-02 1000 Tablets NDC 0555-0869-05 2275 mg: Green, oval, scored tablet. Debossed with 832/2275 on the scored side and stylized barr onthe other side. Available in Bottles of: 100 Tablets NDC 0555-0832-02 1000 Tablets NDC 0555-0832-05 3 mg: Tan, oval, scored tablet. Debossed with 925/3 on the scored side and stylized barr on theother side. Available in Bottles of: 100 Tablets NDC 0555-0925-02 4 mg: 4 mg: Blue, oval, scored tablet. Debossed with 874/4 on the scored side and stylized barron the other side. Available in Bottles of: 100 Tablets 0555-0874-02 1000 Tablets 0555-0874-05 5 mg: Peach, oval, scored tablet. Debossed with 833/5 on the scored side and stylized barr onthe other side. Available in Bottles of: 100 Tablets NDC 0555-0833-02 1000 Tablets NDC 0555-0833-05 6 mg: Teal, oval, scored tablet. Debossed with 926/6 on the scored side and stylized barr on theother side. Available in Bottles of: 100 Tablets NDC 0555-0926-02 7275 mg: Yellow, oval, scored tablet. Debossed with 834/7275 on the scored side and stylized barron the other side. Available in Bottles of: 100 Tablets NDC 0555-0834-02 10 mg: White, oval, scored tablet. Debossed with 835/10 on the scored side and stylized barr onthe other side. Available in Bottles of: 100 Tablets NDC 0555-0835-02 Dispense with a child-resistant closure in a tight, light-resistant container.Protect from light.Store at 20260 to 25260C (68260 to 77260F) [See USP Controlled Room Temperature].
REFERENCES
PACKAGE LABEL.PRINCIPAL DISPLAY PANEL SECTION
DRUG: Warfarin Sodium
GENERIC: Warfarin Sodium
DOSAGE: TABLET
ADMINSTRATION: ORAL
NDC: 24236-353-20
STRENGTH:2 mg
COLOR: purple
SHAPE: OVAL
SCORE: Two even pieces
SIZE: 11 mm
IMPRINT: 100
QTY: 100
INACTIVE INGREDIENT
ANHYDROUS LACTOSE
HYPROMELLOSE
MAGNESIUM STEARATE
STARCH, CORN
FD&C BLUE NO. 2
FD&C RED NO. 40
WARFARIN SODIUM
warfarin sodium tablet |
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