Generic Name: WARFARIN SODIUM
Brand Name: Warfarin Sodium
- Substance Name(s):
- WARFARIN SODIUM
DRUG INTERACTIONS
7 Drugs may interact with warfarin sodium through pharmacodynamic or pharmacokinetic mechanisms. Pharmacodynamic mechanisms for drug interactions with warfarin sodium are synergism (impaired hemostasis, reduced clotting factor synthesis), competitive antagonism (vitamin K), and alteration of the physiologic control loop for vitamin K metabolism (hereditary resistance). Pharmacokinetic mechanisms for drug interactions with warfarin sodium are mainly enzyme induction, enzyme inhibition, and reduced plasma protein binding. It is important to note that some drugs may interact by more than one mechanism. More frequent INR monitoring should be performed when starting or stopping other drugs, including botanicals, or when changing dosages of other drugs, including drugs intended for short-term use (e.g., antibiotics, antifungals, corticosteroids) [ ]. see Boxed Warning Consult the labeling of all concurrently used drugs to obtain further information about interactions with warfarin sodium or adverse reactions pertaining to bleeding. Concomitant use of drugs that increase bleeding risk, antibiotics, antifungals, botanical (herbal) products, and inhibitors and inducers of CYP2C9, 1A2, or 3A4 ( ). • 7 Consult labeling of all concurrently used drugs for complete information about interactions with warfarin sodium or increased risks for bleeding. ( ) • 7 7.1 CYP450 Interactions CYP450 isozymes involved in the metabolism of warfarin include CYP2C9, 2C19, 2C8, 2C18, 1A2, and 3A4. The more potent warfarin -enantiomer is metabolized by CYP2C9 while the -enantiomer is metabolized by CYP1A2 and 3A4. S R Inhibitors of CYP2C9, 1A2, and/or 3A4 have the potential to increase the effect (increase INR) of warfarin by increasing the exposure of warfarin. • Inducers of CYP2C9, 1A2, and/or 3A4 have the potential to decrease the effect (decrease INR) of warfarin by decreasing the exposure of warfarin. • Examples of inhibitors and inducers of CYP2C9, 1A2, and 3A4 are below in ; however, this list should not be considered all-inclusive. Consult the labeling of all concurrently used drugs to obtain further information about CYP450 interaction potential. The CYP450 inhibition and induction potential should be considered when starting, stopping, or changing dose of concomitant medications. Closely monitor INR if a concomitant drug is a CYP2C9, 1A2, and/or 3A4 inhibitor or inducer. Table 2 Table 2: Examples of CYP450 Interactions with Warfarin Enzyme Inhibitors Inducers CYP2C9 amiodarone, capecitabine, cotrimoxazole, etravirine, fluconazole, fluvastatin, fluvoxamine, metronidazole, miconazole, oxandrolone, sulfinpyrazone, tigecycline, voriconazole, zafirlukast aprepitant, bosentan, carbamazepine, phenobarbital, rifampin CYP1A2 acyclovir, allopurinol, caffeine, cimetidine, ciprofloxacin, disulfiram, enoxacin, famotidine, fluvoxamine, methoxsalen, mexiletine, norfloxacin, oral contraceptives, phenylpropanolamine, propafenone, propranolol, terbinafine, thiabendazole, ticlopidine, verapamil, zileuton montelukast, moricizine, omeprazole, phenobarbital, phenytoin, cigarette smoking CYP3A4 alprazolam, amiodarone, amlodipine, amprenavir, aprepitant, atorvastatin, atazanavir, bicalutamide, cilostazol, cimetidine, ciprofloxacin, clarithromycin, conivaptan, cyclosporine, darunavir/ritonavir, diltiazem, erythromycin, fluconazole, fluoxetine, fluvoxamine, fosamprenavir, imatinib, indinavir, isoniazid, itraconazole, ketoconazole, lopinavir/ritonavir, nefazodone, nelfinavir, nilotinib, oral contraceptives, posaconazole, ranitidine, ranolazine, ritonavir, saquinavir, telithromycin, tipranavir, voriconazole, zileuton armodafinil, amprenavir, aprepitant, bosentan, carbamazepine, efavirenz, etravirine, modafinil, nafcillin, phenytoin, pioglitazone, prednisone, rifampin, rufinamide 7.2 Drugs that Increase Bleeding Risk Examples of drugs known to increase the risk of bleeding are presented in . Because bleeding risk is increased when these drugs are used concomitantly with warfarin, closely monitor patients receiving any such drug with warfarin. Table 3 Table 3: Drugs that Can Increase the Risk of Bleeding Drug Class Specific Drugs Anticoagulants argatroban, dabigatran, bivalirudin, desirudin, heparin, lepirudin Antiplatelet Agents aspirin, cilostazol, clopidogrel, dipyridamole, prasugrel, ticlopidine Nonsteroidal Anti-Inflammatory Agents celecoxib, diclofenac, diflunisal, fenoprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, mefenamic acid, naproxen, oxaprozin, piroxicam, sulindac Serotonin Reuptake Inhibitors citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, milnacipran, paroxetine, sertraline, venlafaxine, vilazodone 7.3 Antibiotics and Antifungals There have been reports of changes in INR in patients taking warfarin and antibiotics or antifungals, but clinical pharmacokinetic studies have not shown consistent effects of these agents on plasma concentrations of warfarin. Closely monitor INR when starting or stopping any antibiotic or antifungal in patients taking warfarin. 7.4 Botanical (Herbal) Products and Foods More frequent INR monitoring should be performed when starting or stopping botanicals. Few adequate, well-controlled studies evaluating the potential for metabolic and/or pharmacologic interactions between botanicals and warfarin sodium exist. Due to a lack of manufacturing standardization with botanical medicinal preparations, the amount of active ingredients may vary. This could further confound the ability to assess potential interactions and effects on anticoagulation. Some botanicals may cause bleeding events when taken alone (e.g., garlic and Ginkgo biloba) and may have anticoagulant, antiplatelet, and/or fibrinolytic properties. These effects would be expected to be additive to the anticoagulant effects of warfarin sodium. Conversely, some botanicals may decrease the effects of warfarin sodium (e.g., co-enzyme Q , St. John’s wort, ginseng). Some botanicals and foods can interact with warfarin sodium through CYP450 interactions (e.g., echinacea, grapefruit juice, ginkgo, goldenseal, St. John’s wort). 10 The amount of vitamin K in food may affect therapy with warfarin sodium. Advise patients taking warfarin sodium to eat a normal, balanced diet maintaining a consistent amount of vitamin K. Patients taking warfarin sodium should avoid drastic changes in dietary habits, such as eating large amounts of green leafy vegetables.
OVERDOSAGE
10 10.1 Signs and Symptoms Bleeding (e.g., appearance of blood in stools or urine, hematuria, excessive menstrual bleeding, melena, petechiae, excessive bruising or persistent oozing from superficial injuries, unexplained fall in hemoglobin) is a manifestation of excessive anticoagulation. 10.2 Treatment The treatment of excessive anticoagulation is based on the level of the INR, the presence or absence of bleeding, and clinical circumstances. Reversal of warfarin sodium anticoagulation may be obtained by discontinuing warfarin sodium therapy and, if necessary, by administration of oral or parenteral vitamin K . 1 The use of vitamin K reduces response to subsequent warfarin sodium therapy and patients may return to a pretreatment thrombotic status following the rapid reversal of a prolonged INR. Resumption of warfarin sodium administration reverses the effect of vitamin K, and a therapeutic INR can again be obtained by careful dosage adjustment. If rapid re-anticoagulation is indicated, heparin may be preferable for initial therapy. 1 Prothrombin complex concentrate (PCC), fresh frozen plasma, or activated Factor VII treatment may be considered if the requirement to reverse the effects of warfarin sodium is urgent. A risk of hepatitis and other viral diseases is associated with the use of blood products; PCC and activated Factor VII are also associated with an increased risk of thrombosis. Therefore, these preparations should be used only in exceptional or life-threatening bleeding episodes secondary to warfarin sodium overdosage.
DESCRIPTION
11 Warfarin sodium tablets USP contain warfarin sodium, an anticoagulant that acts by inhibiting vitamin K-dependent coagulation factors. The chemical name of warfarin sodium is 3-(α-acetonylbenzyl)-4-hydroxycoumarin sodium salt, which is a racemic mixture of the – and -enantiomers. Crystalline warfarin sodium is an isopropanol clathrate. Its structural formula may be represented as follows: R S C H NaO M.W. 330.31 19 15 4 Crystalline warfarin sodium occurs as a white, odorless, crystalline powder that is discolored by light. It is very soluble in water, freely soluble in alcohol, and very slightly soluble in chloroform and ether. Each tablet, for oral administration, contains 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg or 10 mg warfarin sodium, USP. In addition, each tablet contains the following inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, lactose monohydrate, magnesium stearate, and microcrystalline cellulose. The 1 mg also contains FD&C red no. 40. The 2 mg also contains FD&C blue no. 2 aluminum lake and FD&C red no. 40 aluminum lake. The 2.5 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 yellow no. 6 aluminum lake, FD&C blue no. 2 aluminum lake, FD&C red no. 40 aluminum lake, and D&C yellow no. 10 aluminum lake. The 4 mg also contains FD&C blue no. 1 aluminum lake and FD&C blue no. 2 aluminum lake. The 5 mg also contains FD&C yellow no. 6 aluminum lake, FD&C red no. 40 aluminum lake and D&C yellow no. 10 aluminum lake. The 6 mg also contains D&C yellow no. 10 aluminum lake and FD&C blue no. 1 aluminum lake. The 7.5 mg also contains FD&C yellow no. 5 (tartrazine) aluminum lake and FD&C red no. 40 aluminum lake. Warfarin Structural Formula
CLINICAL STUDIES
14 14.1 Atrial Fibrillation In five prospective, randomized, controlled clinical trials involving 3711 patients with non-rheumatic AF, warfarin significantly reduced the risk of systemic thromboembolism including stroke (see ). The risk reduction ranged from 60% to 86% in all except one trial (CAFA: 45%), which was stopped early due to published positive results from two of these trials. The incidence of major bleeding in these trials ranged from 0.6% to 2.7% (see ). Table 4 Table 4 Table 4: Clinical Studies of Warfarin in Non-Rheumatic AF Patients All study results of warfarin vs. control are based on intention-to-treat analysis and include ischemic stroke and systemic thromboembolism, excluding hemorrhagic stroke and transient ischemic attacks. N Thromboembolism % Major Bleeding Study Warfarin-Treated Patients Control Patients PT Ratio INR % Risk Reduction -value p Warfarin-Treated Patients Control Patients AFASAK 335 336 1.5 to 2 2.8 to 4.2 60 0.027 0.6 0 SPAF 210 211 1.3 to 1.8 2 to 4.5 67 0.01 1.9 1.9 BAATAF 212 208 1.2 to 1.5 1.5 to 2.7 86 < 0.05 0.9 0.5 CAFA 187 191 1.3 to 1.6 2 to 3 45 0.25 2.7 0.5 SPINAF 260 265 1.2 to 1.5 1.4 to 2.8 79 0.001 2.3 1.5 Trials in patients with both AF and mitral stenosis suggest a benefit from anticoagulation with warfarin sodium [ ]. see Dosage and Administration ( ) 2.2 14.2 Mechanical and Bioprosthetic Heart Valves In a prospective, randomized, open-label, positive-controlled study in 254 patients with mechanical prosthetic heart valves, the thromboembolic-free interval was found to be significantly greater in patients treated with warfarin alone compared with dipyridamole/aspirin-treated patients (p < 0.005) and pentoxifylline/aspirin-treated patients (p < 0.05). The results of this study are presented in . Table 5 Table 5: Prospective, Randomized, Open-Label, Positive-Controlled Clinical Study of Warfarin in Patients with Mechanical Prosthetic Heart Valves Patients Treated With Warfarin Dipyridamole/Aspirin Pentoxifylline/Aspirin Event Thromboembolism 2.2/100 py 8.6/100 py 7.9/100 py Major Bleeding 2.5/100 py 0/100 py 0.9/100 py py = patient years In a prospective, open-label, clinical study comparing moderate (INR 2.65) versus high intensity (INR 9) warfarin therapies in 258 patients with mechanical prosthetic heart valves, thromboembolism occurred with similar frequency in the two groups (4 and 3.7 events per 100 patient years, respectively). Major bleeding was more common in the high intensity group. The results of this study are presented in . Table 6 Table 6: Prospective, Open-Label Clinical Study of Warfarin in Patients with Mechanical Prosthetic Heart Valves Event Moderate Warfarin Therapy INR 2.65 High Intensity Warfarin Therapy INR 9 Thromboembolism 4/100 py 3.7/100 py Major Bleeding 0.95/100 py 2.1/100 py py = patient years In a randomized trial in 210 patients comparing two intensities of warfarin therapy (INR 2 to 2.25 vs. INR 2.5 to 4) for a three month period following tissue heart valve replacement, thromboembolism occurred with similar frequency in the two groups (major embolic events 2% vs. 1.9%, respectively, and minor embolic events 10.8% vs. 10.2%, respectively). Major hemorrhages occurred in 4.6% of patients in the higher intensity INR group compared to zero in the lower intensity INR group. 14.3 Myocardial Infarction WARIS (The Warfarin Re-Infarction Study) was a double-blind, randomized study of 1214 patients 2 to 4 weeks post-infarction treated with warfarin to a target INR of 2.8 to 4.8. The primary endpoint was a composite of total mortality and recurrent infarction. A secondary endpoint of cerebrovascular events was assessed. Mean follow-up of the patients was 37 months. The results for each endpoint separately, including an analysis of vascular death, are provided in . Table 7 Table 7: WARIS – Endpoint Analysis of Separate Events % Risk Warfarin Placebo Reduction Event (N = 607) (N = 607) RR (95% CI) ( -value) p Total Patient Years of Follow-up 2018 1944 Total Mortality 94 (4.7/100 py) 123 (6.3/100 py) 0.76 (0.60, 0.97) 24 (p = 0.030) Vascular Death 82 (4.1/100 py) 105 (5.4/100 py) 0.78 (0.60, 1.02) 22 (p = 0.068) Recurrent MI 82 (4.1/100 py) 124 (6.4/100 py) 0.66 (0.51, 0.85) 34 (p = 0.001) Cerebrovascular Event 20 (1/100 py) 44 (2.3/100 py) 0.46 (0.28, 0.75) 54 (p = 0.002) RR = Relative risk; Risk reduction = (1 – RR); CI = Confidence interval; MI = Myocardial infarction; py = patient years WARIS II (The Warfarin, Aspirin, Re-Infarction Study) was an open-label, randomized study of 3630 patients hospitalized for acute myocardial infarction treated with warfarin to a target INR 2.8 to 4.2, aspirin 160 mg per day, or warfarin to a target INR 2 to 2.5 plus aspirin 75 mg per day prior to hospital discharge. The primary endpoint was a composite of death, nonfatal reinfarction, or thromboembolic stroke. The mean duration of observation was approximately 4 years. The results for WARIS II are provided in . Table 8 Table 8: WARIS II – Distribution of Events According to Treatment Group Event Aspirin (N = 1206) Warfarin (N = 1216) Aspirin plus Warfarin (N = 1208) Rate Ratio (95% CI) -value p No. of Events Major Bleeding Major bleeding episodes were defined as nonfatal cerebral hemorrhage or bleeding necessitating surgical intervention or blood transfusion. 8 33 28 3.35 (ND) The rate ratio is for aspirin plus warfarin as compared with aspirin. ND 4 (ND) The rate ratio is for warfarin as compared with aspirin. ND Minor Bleeding Minor bleeding episodes were defined as non-cerebral hemorrhage not necessitating surgical intervention or blood transfusion. 39 103 133 3.21 (ND) ND 2.55 (ND) ND Composite Endpoints Includes death, nonfatal reinfarction, and thromboembolic cerebral stroke. 241 203 181 0.81 (0.69 to 0.95) 0.03 0.71 (0.60 to 0.83) 0.001 Reinfarction 117 90 69 0.56 (0.41 to 0.78) < 0.001 0.74 (0.55 to 0.98) 0.03 Thromboembolic Stroke 32 17 17 0.52 (0.28 to 0.98) 0.03 0.52 (0.28 to 0.97) 0.03 Death 92 96 95 0.82 CI = confidence interval ND = not determined There were approximately four times as many major bleeding episodes in the two groups receiving warfarin than in the group receiving aspirin alone. Major bleeding episodes were not more frequent among patients receiving aspirin plus warfarin than among those receiving warfarin alone, but the incidence of minor bleeding episodes was higher in the combined therapy group.
HOW SUPPLIED
16 /STORAGE AND HANDLING NDC:54569-5868-0 in a BOTTLE of 30 TABLETS
GERIATRIC USE
8.5 Geriatric Use Of the total number of patients receiving warfarin sodium in controlled clinical trials for which data were available for analysis, 1885 patients (24.4%) were 65 years and older, while 185 patients (2.4%) were 75 years and older. No overall differences in effectiveness or safety were observed between these patients and younger patients, but greater sensitivity of some older individuals cannot be ruled out. Patients 60 years or older appear to exhibit greater than expected INR response to the anticoagulant effects of warfarin [ ]. Warfarin sodium is contraindicated in any unsupervised patient with senility. Observe caution with administration of warfarin sodium to elderly patients in any situation or with any physical condition where added risk of hemorrhage is present. Consider lower initiation and maintenance doses of warfarin sodium in elderly patients [ ]. see Clinical Pharmacology ( ) 12.3 see Dosage and Administration ( , ) 2.2 2.3
DOSAGE FORMS AND STRENGTHS
3 Warfarin Sodium Tablets USP, 1 mg are available as pink, capsule-shaped, biconvex scored tablets, debossed with TV/1 on the scored side and 1712 on the other side. Warfarin Sodium Tablets USP, 2 mg are available as lavender, capsule-shaped, biconvex scored tablets, debossed with TV/2 on the scored side and 1713 on the other side. Warfarin Sodium Tablets USP, 2.5 mg are available as green, capsule-shaped, biconvex scored tablets, debossed with TV/2 / on the scored side and 1714 on the other side. 1 2 Warfarin Sodium Tablets USP, 3 mg are available as tan, capsule-shaped, biconvex scored tablets, debossed with TV/3 on the scored side and 1715 on the other side. Warfarin Sodium Tablets USP, 4 mg are available as blue, capsule-shaped, biconvex scored tablets, debossed with TV/4 on the scored side and 1716 on the other side. Warfarin Sodium Tablets USP, 5 mg are available as peach, capsule-shaped, biconvex scored tablets, debossed with TV/5 on the scored side and 1721 on the other side. Warfarin Sodium Tablets USP, 6 mg are available as teal, capsule-shaped, biconvex scored tablets, debossed with TV/6 on the scored side and 1718 on the other side. Warfarin Sodium Tablets USP, 7.5 mg are available as yellow, capsule-shaped, biconvex scored tablets, debossed with TV/7 / on the scored side and 1719 on the other side. 1 2 Warfarin Sodium Tablets USP, 10 mg are available as white, capsule-shaped, biconvex scored tablets, debossed with TV/10 on the scored side and 1720 on the other side. Scored tablets: 1, 2, 2.5, 3, 4, 5, 6, 7.5, or 10 mg ( ) • 3
MECHANISM OF ACTION
12.1 Mechanism of Action Warfarin acts by inhibiting the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and the anticoagulant proteins C and S. Vitamin K is an essential cofactor for the post ribosomal synthesis of the vitamin K-dependent clotting factors. Vitamin K promotes the biosynthesis of γ-carboxyglutamic acid residues in the proteins that are essential for biological activity. Warfarin is thought to interfere with clotting factor synthesis by inhibition of the C1 subunit of vitamin K epoxide reductase (VKORC1) enzyme complex, thereby reducing the regeneration of vitamin K epoxide [ ]. 1 see Clinical Pharmacology ( ) 12.5
INDICATIONS AND USAGE
1 Warfarin sodium tablets are indicated for: Prophylaxis and treatment of venous thrombosis and its extension, pulmonary embolism (PE). • Prophylaxis and treatment of thromboembolic complications associated with atrial fibrillation (AF) and/or cardiac valve replacement. • Reduction in the risk of death, recurrent myocardial infarction (MI), and thromboembolic events such as stroke or systemic embolization after myocardial infarction. • Limitations of Use Warfarin sodium tablets have no direct effect on an established thrombus, nor does it reverse ischemic tissue damage. Once a thrombus has occurred, however, the goals of anticoagulant treatment are to prevent further extension of the formed clot and to prevent secondary thromboembolic complications that may result in serious and possibly fatal sequelae. Warfarin sodium tablets are a vitamin K antagonist indicated for: Prophylaxis and treatment of venous thrombosis and its extension, pulmonary embolism ( ) • 1 Prophylaxis and treatment of thromboembolic complications associated with atrial fibrillation and/or cardiac valve replacement ( ) • 1 Reduction in the risk of death, recurrent myocardial infarction, and thromboembolic events such as stroke or systemic embolization after myocardial infarction ( ) • 1 Limitations of Use Warfarin sodium tablets have no direct effect on an established thrombus, nor does it reverse ischemic tissue damage. ( ) 1
PEDIATRIC USE
8.4 Pediatric Use Adequate and well-controlled studies with warfarin sodium have not been conducted in any pediatric population, and the optimum dosing, safety, and efficacy in pediatric patients is unknown. Pediatric use of warfarin sodium is based on adult data and recommendations, and available limited pediatric data from observational studies and patient registries. Pediatric patients administered warfarin sodium should avoid any activity or sport that may result in traumatic injury. The developing hemostatic system in infants and children results in a changing physiology of thrombosis and response to anticoagulants. Dosing of warfarin in the pediatric population varies by patient age, with infants generally having the highest, and adolescents having the lowest milligram per kilogram dose requirements to maintain target INRs. Because of changing warfarin requirements due to age, concomitant medications, diet, and existing medical condition, target INR ranges may be difficult to achieve and maintain in pediatric patients, and more frequent INR determinations are recommended. Bleeding rates varied by patient population and clinical care center in pediatric observational studies and patient registries. Infants and children receiving vitamin K-supplemented nutrition, including infant formulas, may be resistant to warfarin therapy, while human milk-fed infants may be sensitive to warfarin therapy.
PREGNANCY
8.1 Pregnancy Risk Summary Warfarin sodium is contraindicated in women who are pregnant except in pregnant women with mechanical heart valves, who are at high risk of thromboembolism, and for whom the benefits of warfarin sodium may outweigh the risks [ ]. Warfarin sodium can cause fetal harm. Exposure to warfarin during the first trimester of pregnancy caused a pattern of congenital malformations in about 5% of exposed offspring. Because these data were not collected in adequate and well-controlled studies, this incidence of major birth defects are not an adequate basis for comparison to the estimated incidences in the control group or the U.S. general population and may not reflect the incidences observed in practice. Consider the benefits and risks of warfarin sodium and possible risks to the fetus when prescribing warfarin sodium to a pregnant woman. see Warnings and Precautions ( ) 5.5 In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Clinical Considerations Fetal/Neonatal Adverse Reactions In humans, warfarin crosses the placenta, and concentrations in fetal plasma approach the maternal values. Exposure to warfarin during the first trimester of pregnancy caused a pattern of congenital malformations in about 5% of exposed offspring. Warfarin embryopathy is characterized by nasal hypoplasia with or without stippled epiphyses (chondrodysplasia punctata) and growth retardation (including low birth weight). Central nervous system and eye abnormalities have also been reported, including dorsal midline dysplasia characterized by agenesis of the corpus callosum, Dandy-Walker malformation, midline cerebellar atrophy, and ventral midline dysplasia characterized by optic atrophy. Mental retardation, blindness, schizencephaly, microcephaly, hydrocephalus, and other adverse pregnancy outcomes have been reported following warfarin exposure during the ]. second and third trimesters of pregnancy [ see Contraindications ( ) 4
BOXED WARNING
WARNING: BLEEDING RISK Warfarin sodium can cause major or fatal bleeding . • [see Warnings and Precautions ( )] 5.1 Perform regular monitoring of INR in all treated patients . • [see Dosage and Administration ( )] 2.1 Drugs, dietary changes, and other factors affect INR levels achieved with warfarin sodium therapy . • [see Drug Interactions ( )] 7 Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding . • [see Patient Counseling Information ( )] 17 WARNING: BLEEDING RISK See full prescribing information for complete boxed warning. Warfarin sodium can cause major or fatal bleeding. ( ) • 5.1 Perform regular monitoring of INR in all treated patients. ( ) • 2.1 Drugs, dietary changes, and other factors affect INR levels achieved with warfarin sodium therapy. ( ) • 7 Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding. ( ) • 17
WARNING AND CAUTIONS
5 WARNINGS AND PRECAUTIONS The 7.5 mg tablets contain FD&C Yellow No. 5 (tartrazine), which may cause allergic-type reactions (including bronchial asthma) in certain susceptible individuals. Although the overall incidence of FD&C Yellow No. 5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity. Tissue necrosis: Necrosis or gangrene of skin or other tissues can occur, with severe cases requiring debridement or amputation. Discontinue warfarin sodium and consider alternative anticoagulants if necessary. ( ) • 5.2 Systemic atheroemboli and cholesterol microemboli: Some cases have progressed to necrosis or death. Discontinue warfarin sodium if such emboli occur. ( ) • 5.3 Heparin-induced thrombocytopenia (HIT): Initial therapy with warfarin sodium in HIT has resulted in cases of amputation and death. Warfarin sodium may be considered after platelet count has normalized. ( ) • 5.4 Pregnant women with mechanical heart valves: warfarin sodium may cause fetal harm; however, the benefits may outweigh the risks. ( ) • 5.5 5.1 Hemorrhage Warfarin sodium can cause major or fatal bleeding. Bleeding is more likely to occur within the first month. Risk factors for bleeding include high intensity of anticoagulation (INR > 4), age greater than or equal to 65, history of highly variable INRs, history of gastrointestinal bleeding, hypertension, cerebrovascular disease, anemia, malignancy, trauma, renal impairment, certain genetic factors [ ], certain concomitant drugs [ ], and long duration of warfarin therapy. see Clinical Pharmacology ( ) 12.5 see Drug Interactions ( ) 7 Perform regular monitoring of INR in all treated patients. Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shortest duration of therapy appropriate for the clinical condition. However, maintenance of INR in the therapeutic range does not eliminate the risk of bleeding. Drugs, dietary changes, and other factors affect INR levels achieved with warfarin sodium therapy. Perform more frequent INR monitoring when starting or stopping other drugs, including botanicals, or when changing dosages of other drugs [ ]. see Drug Interactions ( ) 7 Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding [ ]. see Patient Counseling Information ( ) 17 5.2 Tissue Necrosis Necrosis and/or gangrene of skin and other tissues is an uncommon but serious risk (< 0.1%). Necrosis may be associated with local thrombosis and usually appears within a few days of the start of warfarin sodium therapy. In severe cases of necrosis, treatment through debridement or amputation of the affected tissue, limb, breast, or penis has been reported. Careful clinical evaluation is required to determine whether necrosis is caused by an underlying disease. Although various treatments have been attempted, no treatment for necrosis has been considered uniformly effective. Discontinue warfarin sodium therapy if necrosis occurs. Consider alternative drugs if continued anticoagulation therapy is necessary. 5.3 Systemic Atheroemboli and Cholesterol Microemboli Anticoagulation therapy with warfarin sodium may enhance the release of atheromatous plaque emboli. Systemic atheroemboli and cholesterol microemboli can present with a variety of signs and symptoms depending on the site of embolization. The most commonly involved visceral organs are the kidneys followed by the pancreas, spleen, and liver. Some cases have progressed to necrosis or death. A distinct syndrome resulting from microemboli to the feet is known as “purple toes syndrome.” Discontinue warfarin sodium therapy if such phenomena are observed. Consider alternative drugs if continued anticoagulation therapy is necessary. 5.4 Limb Ischemia, Necrosis, and Gangrene in Patients with HIT and HITTS Do not use warfarin sodium as initial therapy in patients with heparin-induced thrombocytopenia (HIT) and with heparin-induced thrombocytopenia with thrombosis syndrome (HITTS). Cases of limb ischemia, necrosis, and gangrene have occurred in patients with HIT and HITTS when heparin treatment was discontinued and warfarin therapy was started or continued. In some patients, sequelae have included amputation of the involved area and/or death. Treatment with warfarin sodium may be considered after the platelet count has normalized. 5.5 Use in Pregnant Women with Mechanical Heart Valves Warfarin sodium can cause fetal harm when administered to a pregnant woman. While warfarin sodium is contraindicated during pregnancy, the potential benefits of using warfarin sodium may outweigh the risks for pregnant women with mechanical heart valves at high risk of thromboembolism. In those individual situations, the decision to initiate or continue warfarin sodium should be reviewed with the patient, taking into consideration the specific risks and benefits pertaining to the individual patient’s medical situation, as well as the most current medical guidelines. Warfarin sodium exposure during pregnancy causes a recognized pattern of major congenital malformations (warfarin embryopathy and fetotoxicity), fatal fetal hemorrhage, and an increased risk of spontaneous abortion and fetal mortality. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus [ ]. see Use in Specific Populations ( ) 8.1 5.6 Other Clinical Settings with Increased Risks In the following clinical settings, the risks of warfarin sodium therapy may be increased: Moderate to severe hepatic impairment • Infectious diseases or disturbances of intestinal flora (e.g., sprue, antibiotic therapy) • Use of an indwelling catheter • Severe to moderate hypertension • Deficiency in protein C-mediated anticoagulant response: warfarin sodium reduces the synthesis of the naturally occurring anticoagulants, protein C and protein S. Hereditary or acquired deficiencies of protein C or its cofactor, protein S, have been associated with tissue necrosis following warfarin administration. Concomitant anticoagulation therapy with heparin for 5 to 7 days during initiation of therapy with warfarin sodium may minimize the incidence of tissue necrosis in these patients. • Eye surgery: In cataract surgery, warfarin sodium use was associated with a significant increase in minor complications of sharp needle and local anesthesia block but not associated with potentially sight-threatening operative hemorrhagic complications. As warfarin sodium cessation or reduction may lead to serious thromboembolic complications, the decision to discontinue warfarin sodium before a relatively less invasive and complex eye surgery, such as lens surgery, should be based upon the risks of anticoagulant therapy weighed against the benefits. • Polycythemia vera • Vasculitis • Diabetes mellitus • 5.7 Endogenous Factors Affecting INR The following factors may be responsible for INR response: diarrhea, hepatic disorders, poor nutritional state, steatorrhea, or vitamin K deficiency. increased The following factors may be responsible for INR response: increased vitamin K intake or hereditary warfarin resistance. decreased
INFORMATION FOR PATIENTS
17 PATIENT COUNSELING INFORMATION Advise the patient to read the FDA-approved patient labeling (Medication Guide). Advise patients to: Tell their physician if they fall often as this may increase their risk for complications. • Strictly adhere to the prescribed dosage schedule. Do not take or discontinue any other drug, including salicylates (e.g., aspirin and topical analgesics), other over-the-counter drugs, and botanical (herbal) products except on advice of your physician. • Notify their physician immediately if any unusual bleeding or symptoms occur. Signs and symptoms of bleeding include: pain, swelling or discomfort, prolonged bleeding from cuts, increased menstrual flow or vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or dark brown urine, red or tar black stools, headache, dizziness, or weakness. • Contact their doctor • − immediately if they think they are pregnant − to discuss pregnancy planning − if they are considering breastfeeding Avoid any activity or sport that may result in traumatic injury. • Obtain prothrombin time tests and make regular visits to their physician or clinic to monitor therapy. • Carry identification stating that they are taking warfarin sodium. • If the prescribed dose of warfarin sodium is missed, take the dose as soon as possible on the same day but do not take a double dose of warfarin sodium the next day to make up for missed doses. • Eat a normal, balanced diet to maintain a consistent intake of vitamin K. Avoid drastic changes in dietary habits, such as eating large amounts of leafy, green vegetables. • Contact their physician to report any serious illness, such as severe diarrhea, infection, or fever. • Be aware that if therapy with warfarin sodium is discontinued, the anticoagulant effects of warfarin sodium may persist for about 2 to 5 days. • Manufactured In Croatia By: PLIVA HRVATSKA d.o.o. Zagreb, Croatia Manufactured For: TEVA PHARMACEUTICALS USA, INC. North Wales, PA 19454 Rev. A 11/2015
DOSAGE AND ADMINISTRATION
2 Individualize dosing regimen for each patient, and adjust based on INR response. ( , ) • 2.1 2.2 Knowledge of genotype can inform initial dose selection. ( ) • 2.3 Monitoring: Obtain daily INR determinations upon initiation until stable in the therapeutic range. Obtain subsequent INR determinations every 1 to 4 weeks. ( ) • 2.4 Review conversion instructions from other anticoagulants. ( ) • 2.8 2.2 Recommended Target INR Ranges and Durations for Individual Indications An INR of greater than 4 appears to provide no additional therapeutic benefit in most patients and is associated with a higher risk of bleeding. Venous Thromboembolism (including deep venous thrombosis [DVT] and PE) Adjust the warfarin dose to maintain a target INR of 2.5 (INR range, 2 to 3) for all treatment durations. The duration of treatment is based on the indication as follows: For patients with a DVT or PE secondary to a transient (reversible) risk factor, treatment with warfarin for 3 months is recommended. • For patients with an unprovoked DVT or PE, treatment with warfarin is recommended for at least 3 months. After 3 months of therapy, evaluate the risk-benefit ratio of long-term treatment for the individual patient. • For patients with two episodes of unprovoked DVT or PE, long-term treatment with warfarin is recommended. For a patient receiving long-term anticoagulant treatment, periodically reassess the risk-benefit ratio of continuing such treatment in the individual patient. • Atrial Fibrillation In patients with non-valvular AF, anticoagulate with warfarin to target INR of 2.5 (range, 2 to 3). In patients with non-valvular AF that is persistent or paroxysmal and at high risk of stroke (i.e., having any of the following features: prior ischemic stroke, transient ischemic attack, or systemic embolism, or 2 of the following risk factors: age greater than 75 years, moderately or severely impaired left ventricular systolic function and/or heart failure, history of hypertension, or diabetes mellitus), long-term anticoagulation with warfarin is recommended. • In patients with non-valvular AF that is persistent or paroxysmal and at an intermediate risk of ischemic stroke (i.e., having 1 of the following risk factors: age greater than 75 years, moderately or severely impaired left ventricular systolic function and/or heart failure, history of hypertension, or diabetes mellitus), long-term anticoagulation with warfarin is recommended. • For patients with AF and mitral stenosis, long-term anticoagulation with warfarin is recommended. • For patients with AF and prosthetic heart valves, long-term anticoagulation with warfarin is recommended; the target INR may be increased and aspirin added depending on valve type and position, and on patient factors. • Mechanical and Bioprosthetic Heart Valves For patients with a bileaflet mechanical valve or a Medtronic Hall (Minneapolis, MN) tilting disk valve in the aortic position who are in sinus rhythm and without left atrial enlargement, therapy with warfarin to a target INR of 2.5 (range, 2 to 3) is recommended. • For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, therapy with warfarin to a target INR of 3 (range, 2.5 to 3.5) is recommended. • For patients with caged ball or caged disk valves, therapy with warfarin to a target INR of 3 (range, 2.5 to 3.5) is recommended. • For patients with a bioprosthetic valve in the mitral position, therapy with warfarin to a target INR of 2.5 (range, 2 to 3) for the first 3 months after valve insertion is recommended. If additional risk factors for thromboembolism are present (AF, previous thromboembolism, left ventricular dysfunction), a target INR of 2.5 (range 2 to 3) is recommended. • Post-Myocardial Infarction For high-risk patients with MI (e.g., those with a large anterior MI, those with significant heart failure, those with intracardiac thrombus visible on transthoracic echocardiography, those with AF, and those with a history of a thromboembolic event), therapy with combined moderate-intensity (INR, 2 to 3) warfarin plus low-dose aspirin (≤ 100 mg/day) for at least 3 months after the MI is recommended. • Recurrent Systemic Embolism and Other Indications Oral anticoagulation therapy with warfarin has not been fully evaluated by clinical trials in patients with valvular disease associated with AF, patients with mitral stenosis, and patients with recurrent systemic embolism of unknown etiology. However, a moderate dose regimen (INR 2 to 3) may be used for these patients. 2.3 Initial and Maintenance Dosing The appropriate initial dosing of warfarin sodium tablets varies widely for different patients. Not all factors responsible for warfarin dose variability are known, and the initial dose is influenced by: Clinical factors including age, race, body weight, sex, concomitant medications, and comorbidities • Genetic factors (CYP2C9 and VKORC1 genotypes) [ ]. • see Clinical Pharmacology ( ) 12.5 Select the initial dose based on the expected maintenance dose, taking into account the above factors. Modify this dose based on consideration of patient-specific clinical factors. Consider lower initial and maintenance doses for elderly and/or debilitated patients and in Asian patients [ ]. Routine use of loading doses is not recommended as this practice may increase hemorrhagic and other complications and does not offer more rapid protection against clot formation. see Use in Specific Populations ( ) and Clinical Pharmacology ( ) 8.5 12.3 Individualize the duration of therapy for each patient. In general, anticoagulant therapy should be continued until the danger of thrombosis and embolism has passed [ ]. see Dosage and Administration ( ) 2.2 Dosing Recommendations without Consideration of Genotype If the patient’s CYP2C9 and VKORC1 genotypes are not known, the initial dose of warfarin sodium tablets is usually 2 to 5 mg once daily. Determine each patient’s dosing needs by close monitoring of the INR response and consideration of the indication being treated. Typical maintenance doses are 2 to 10 mg once daily. Dosing Recommendations with Consideration of Genotype displays three ranges of expected maintenance warfarin sodium tablets doses observed in subgroups of patients having different combinations of CYP2C9 and VKORC1 gene variants [ ]. If the patient’s CYP2C9 and/or VKORC1 genotype are known, consider these ranges in choosing the initial dose. Patients with CYP2C9 *1/*3, *2/*2, *2/*3, and *3/*3 may require more prolonged time (> 2 to 4 weeks) to achieve maximum INR effect for a given dosage regimen than patients without these CYP variants. Table 1 see Clinical Pharmacology ( ) 12.5 Table 1: Three Ranges of Expected Maintenance Warfarin Sodium Tablets Daily Doses Based on CYP2C9 and VKORC1 Genotypes Ranges are derived from multiple published clinical studies. VKORC1 −1639G > A (rs9923231) variant is used in this table. Other co-inherited VKORC1 variants may also be important determinants of warfarin dose. VKORC1 CYP2C9 *1/*1 *1/*2 *1/*3 *2/*2 *2/*3 *3/*3 GG 5 to 7 mg 5 to 7 mg 3 to 4 mg 3 to 4 mg 3 to 4 mg 0.5 to 2 mg AG 5 to 7 mg 3 to 4 mg 3 to 4 mg 3 to 4 mg 0.5 to 2 mg 0.5 to 2 mg AA 3 to 4 mg 3 to 4 mg 0.5 to 2 mg 0.5 to 2 mg 0.5 to 2 mg 0.5 to 2 mg 2.4 Monitoring to Achieve Optimal Anticoagulation Warfarin sodium tablets have a narrow therapeutic range (index), and their action may be affected by factors such as other drugs and dietary vitamin K. Therefore, anticoagulation must be carefully monitored during warfarin sodium tablets therapy. Determine the INR daily after the administration of the initial dose until INR results stabilize in the therapeutic range. After stabilization, maintain dosing within the therapeutic range by performing periodic INRs. The frequency of performing INR should be based on the clinical situation but generally acceptable intervals for INR determinations are 1 to 4 weeks. Perform additional INR tests when other warfarin products are interchanged with warfarin sodium tablets, as well as whenever other medications are initiated, discontinued, or taken irregularly. Heparin, a common concomitant drug, increases the INR [ ]. see Dosage and Administration ( ) and Drug Interactions ( ) 2.8 7 Determinations of whole blood clotting and bleeding times are not effective measures for monitoring of warfarin sodium tablets therapy. 2.5 Missed Dose The anticoagulant effect of warfarin sodium tablets persists beyond 24 hours. If a patient misses a dose of warfarin sodium tablets at the intended time of day, the patient should take the dose as soon as possible on the same day. The patient should not double the dose the next day to make up for a missed dose. 2.7 Treatment During Dentistry and Surgery Some dental or surgical procedures may necessitate the interruption or change in the dose of warfarin sodium tablets therapy. Consider the benefits and risks when discontinuing warfarin sodium tablets even for a short period of time. Determine the INR immediately prior to any dental or surgical procedure. In patients undergoing minimally invasive procedures who must be anticoagulated prior to, during, or immediately following these procedures, adjusting the dosage of warfarin sodium tablets to maintain the INR at the low end of the therapeutic range may safely allow for continued anticoagulation. 2.8 Conversion From Other Anticoagulants Heparin Since the full anticoagulant effect of warfarin sodium tablets is not achieved for several days, heparin is preferred for initial rapid anticoagulation. During initial therapy with warfarin sodium tablets, the interference with heparin anticoagulation is of minimal clinical significance. Conversion to warfarin sodium tablets may begin concomitantly with heparin therapy or may be delayed 3 to 6 days. To ensure therapeutic anticoagulation, continue full dose heparin therapy and overlap warfarin sodium tablets therapy with heparin for 4 to 5 days and until warfarin sodium tablets has produced the desired therapeutic response as determined by INR, at which point heparin may be discontinued. As heparin may affect the INR, patients receiving both heparin and warfarin sodium tablets should have INR monitoring at least: 5 hours after the last intravenous bolus dose of heparin, or • 4 hours after cessation of a continuous intravenous infusion of heparin, or • 24 hours after the last subcutaneous heparin injection. • Warfarin sodium tablets may increase the activated partial thromboplastin time (aPTT) test, even in the absence of heparin. A severe elevation (> 50 seconds) in aPTT with an INR in the desired range has been identified as an indication of increased risk of postoperative hemorrhage. Other Anticoagulants Consult the labeling of other anticoagulants for instructions on conversion to warfarin sodium tablets.