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)].
Warfarin was not present in human milk from mothers treated with warfarin from a limited published study. Because of the potential for serious adverse reactions, including bleeding in a breastfed infant, consider the developmental and health benefits of breastfeeding along with the mother’s clinical need for COUMADIN and any potential adverse effects on the breastfed infant from COUMADIN or from the underlying maternal condition before prescribing COUMADIN to a lactating woman.
Monitor breastfeeding infants for bruising or bleeding.
Based on published data in 15 nursing mothers, warfarin was not detected in human milk. Among the 15 full-term newborns, 6 nursing infants had documented prothrombin times within the expected range. Prothrombin times were not obtained for the other 9 nursing infants. Effects in premature infants have not been evaluated.
COUMADIN can cause fetal harm [see Use in Specific Populations (8.1)].
Verify the pregnancy status of females of reproductive potential prior to initiating COUMADIN therapy.
Advise females of reproductive potential to use effective contraception during treatment and for at least 1 month after the final dose of COUMADIN.
Adequate and well-controlled studies with COUMADIN have not been conducted in any pediatric population, and the optimum dosing, safety, and efficacy in pediatric patients is unknown. Pediatric use of COUMADIN is based on adult data and recommendations, and available limited pediatric data from observational studies and patient registries. Pediatric patients administered COUMADIN 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.
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 [see Clinical Pharmacology (12.3)]. COUMADIN is contraindicated in any unsupervised patient with senility. Conduct more frequent monitoring for bleeding with administration of COUMADIN 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 COUMADIN in elderly patients [see Dosage and Administration (2.2, 2.3)].
Renal clearance is considered to be a minor determinant of anticoagulant response to warfarin. No dosage adjustment is necessary for patients with renal impairment. Instruct patients with renal impairment taking warfarin to monitor their INR more frequently [see Warnings and Precautions (5.4)].
Hepatic impairment can potentiate the response to warfarin through impaired synthesis of clotting factors and decreased metabolism of warfarin. Conduct more frequent monitoring for bleeding when using COUMADIN in these patients.
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.
The treatment of excessive anticoagulation is based on the level of the INR, the presence or absence of bleeding, and clinical circumstances. Reversal of COUMADIN anticoagulation may be obtained by discontinuing COUMADIN therapy and, if necessary, by administration of oral or parenteral vitamin K1 .
The use of vitamin K1 reduces response to subsequent COUMADIN therapy and patients may return to a pretreatment thrombotic status following the rapid reversal of a prolonged INR. Resumption of COUMADIN 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.
Prothrombin complex concentrate (PCC), fresh frozen plasma, or activated Factor VII treatment may be considered if the requirement to reverse the effects of COUMADIN 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 COUMADIN overdosage.
COUMADIN (warfarin sodium) tablets 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 R — and S -enantiomers. Crystalline warfarin sodium is an isopropanol clathrate. Its empirical formula is C19 H15 NaO4 , and its structural formula is represented by the following:
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.
COUMADIN tablets for oral use also contain:
Lactose, starch, and magnesium stearate
D&C Red No. 6 Barium Lake
FD&C Blue No. 2 Aluminum Lake andFD&C Red No. 40 Aluminum Lake
D&C Yellow No. 10 Aluminum Lake andFD&C Blue No. 1 Aluminum Lake
FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake, and FD&C Red No. 40 Aluminum Lake
FD&C Blue No. 1 Aluminum Lake
FD&C Yellow No. 6 Aluminum Lake
FD&C Yellow No. 6 Aluminum Lake andFD&C Blue No. 1 Aluminum Lake
D&C Yellow No. 10 Aluminum Lake andFD&C Yellow No. 6 Aluminum Lake
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