OVERDOSE
Signs and Symptoms: Suspected
or overt abnormal bleeding (e.g., appearance of blood
in stools or urine, hematuria, excessive menstrual bleeding,
melena, petechiae, excessive bruising or persistent oozing
from superficial injuries) are early manifestations of
anticoagulation beyond a safe and satisfactory level.
Treatment: Excessive anticoagulation,
with or without bleeding, may be controlled by discontinuing
warfarin sodium therapy and if necessary, by administration
of oral or parenteral vitamin K1. (Please see recommendations
accompanying vitamin K1preparations prior to use.)
Such use of vitamin K1 reduces response to subsequent
warfarin sodium therapy. Patients may return to a pretreatment
thrombotic status following the rapid reversal of a prolonged
PT/INR . Resumption of warfarin sodium administration
reverses the effect of vitamin K, and a therapeutic PT/INR
can again be obtained by careful dosage adjustment. If
rapid anticoagulation is indicated, heparin may be preferable
for initial therapy.
If minor bleeding progresses to major bleeding, give
5 to 25 mg (rarely up to 50 mg) parenteral vitamin K1.
In emergency situations of severe hemorrhage, clotting
factors can be returned to normal by administering 200
to 500 ml of fresh whole blood or fresh frozen plasma,
or by giving commercial Factor IX complex.
A risk of hepatitis and other viral diseases is associated
with the use of these blood products; Factor IX complex
is 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.
Purified Factor IX preparations should not be used because
they cannot increase the levels of prothrombin, Factor
VII and Factor X which are also depressed along with the
levels of Factor IX as a result of warfarin sodium treatment.
Packed red blood cells may also be given if significant
blood loss has occurred. Infusions of blood or plasma
should be monitored carefully to avoid precipitating pulmonary
edema in elderly patients or patients with heart disease.
CONTRAINDICATIONS
Anticoagulation is contraindicated in any localized or
general physical condition or personal circumstance in
which the hazard of hemorrhage might be greater than the
potential clinical benefits of anticoagulation, such as:
Pregnancy: Warfarin sodium
is contraindicated in women who are or may become pregnant
because the drug passes through the placental barrier
and may cause fatal hemorrhage to the fetus in utero.
Furthermore, there have been reports of birth malformations
in children born to mothers who have been treated with
warfarin sodium during pregnancy.
Embryopathy characterized by nasal hypoplasia with or
without stippled epiphyses (chondrodysplasia punctata)
has been reported in pregnant women exposed to warfarin
sodium during the first trimester. Central nervous system
abnormalities also have been reported, including dorsal
midline dysplasia characterized by agenesis of the corpus
callosum, Dandy-Walker malformation, and midline cerebellar
atrophy. Ventral midline dysplasia, characterized by optic
atrophy, and eye abnormalities have been observed. Mental
retardation, blindness, and other central nervous system
abnormalities have been reported in association with second
and third trimester exposure. Although rare, teratogenic
reports following in utero exposure to warfarin sodium
include urinary tract anomalies such as single kidney,
asplenia, anencephaly, spina bifida, cranial nerve palsy,
hydrocephalus, cardiac defects and congenital heart disease,
polydactyly, deformities of toes, diaphragmatic hernia,
and corneal leukoma, cleft palate, cleft lip, schizencephaly,
and microcephaly.
Spontaneous abortion and still birth are known to occur
and a higher risk of fetal mortality is associated with
the use of warfarin sodium. Low birth weight and growth
retardation have also been reported.
Women of childbearing potential who are candidates for
anticoagulant therapy should be carefully evaluated and
the indications critically reviewed with the patient.
If the patient becomes pregnant while taking this drug,
she should be apprised of the potential risks to the fetus,
and the possibility of termination of the pregnancy should
be discussed in light of those risks.
Hemorrhagic tendencies or blood dyscrasias.
Recent or contemplated surgery of:
(1) central nervous system;
(2) eye;
(3) traumatic surgery resulting in large
open surfaces.
Bleeding tendencies associated with active ulceration
or overt bleeding of:
(1) gastrointestinal, genitourinary
or respiratory tracts;
(2) cerebrovascular hemorrhage;
(3) aneurysms-cerebral, dissecting aorta;
(4) pericarditis and pericardial effusions;
(5) bacterial endocarditis.
Threatened abortion ,eclampsia, and
preeclampsia
Inadequate laboratory facilities
Unsupervised patients with senility ,
alcoholism, psychosis, or lack of patient cooperation
Spinal puncture and other diagnostic
or therapeutic procedures with potential for uncontrollable
bleeding.
Miscellaneous: major regional,
lumbar block anesthesia, and malignant hypertension.
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