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Coumadin, Jantoven
Classification
Therapeutic: anticoagulants
Pharmacologic: coumarins
Pregnancy Category X
controlled hypertension; OB: Crosses placenta and may cause fatal hemorrhage in
the fetus. May also cause congenital malformation.
Use Cautiously in: Malignancy; Patients with history of ulcer or liver disease; History of poor compliance; Women with childbearing potential; Asian patients or
those who carry the CYP2C9*2 allele and/or the CYP2C9*3 allele, or with the VKORC1
AA genotype (qrisk of bleeding with standard dosing; lower initial doses should be
considered); Pedi: Has been used safely but may require more frequent PT/INR assessments; Geri: Due to greater than expected anticoagulant response, initiate and
maintain at lower doses.
Indications
Adverse Reactions/Side Effects
GI: cramps, nausea. Derm: dermal necrosis. Hemat: BLEEDING. Misc: fever.
High Alert
warfarin (war-fa-rin)
Prophylaxis and treatment of: Venous thrombosis, Pulmonary embolism, Atrial fibrillation with embolization. Management of myocardial infarction: Decreases risk of
death, Decreases risk of subsequent MI, Decreases risk of future thromboembolic
events. Prevention of thrombus formation and embolization after prosthetic valve
placement.
Interactions
Drug-Drug: Abciximab, androgens, capecitabine, cefotetan, chloram-
ROUTE
ONSET
PEAK
DURATION
phenicol, clopidogrel, disulfiram, fluconazole, fluoroquinolones, itraconazole, metronidazole (including vaginal use), thrombolytics, eptifibatide, tirofiban, ticlopidine, sulfonamides, quinidine, quinine, NSAIDs, valproates,
and aspirin mayqthe response to warfarin andqthe risk of bleeding. Chronic use
of acetaminophen mayqthe risk of bleeding. Chronic alcohol ingestion maypaction of warfarin; if chronic alcohol abuse results in significant liver damage, action
of warfarin may beqdue topproduction of clotting factor. Acute alcohol ingestion
mayqaction of warfarin. Barbiturates, carbamazepine, rifampin, and hormonal contraceptives containing estrogen maypthe anticoagulant response to
warfarin. Many other drugs may affect the activity of warfarin.
Drug-Natural Products: St. John’s wortpeffect.qbleeding risk with anise,
arnica, chamomile, clove, dong quai, fenugreek, feverfew, garlic, ginger,
ginkgo, Panax ginseng, licorice, and others.
Drug-Food: Ingestion of large quantities of foods high in vitamin K content
may antagonize the anticoagulant effect of warfarin.
PO, IV
36–72 hr
5–7 days†
2–5 days‡
Route/Dosage
Action
Interferes with hepatic synthesis of vitamin K-dependent clotting factors (II, VII, IX,
and X). Therapeutic Effects: Prevention of thromboembolic events.
Pharmacokinetics
Absorption: Well absorbed from the GI tract after oral administration.
Distribution: Crosses the placenta but does not enter breast milk.
Protein Binding: 99%.
Metabolism and Excretion: Metabolized by the liver.
Half-life: 42 hr.
TIME/ACTION PROFILE (effects on coagulation tests)
† At a constant dose
‡ After discontinuation
Contraindications/Precautions
Contraindicated in: Uncontrolled bleeding; Open wounds; Active ulcer disease;
Recent brain, eye, or spinal cord injury or surgery; Severe liver or kidney disease; Un⫽ Canadian drug name.
⫽ Genetic Implication.
PO, IV (Adults): 2– 5 mg/day for 2– 4 days; then adjust daily dose by results of
INR. Initiate therapy with lower doses in geriatric or debilitated patients or in Asian
patients or those with CYP2C9*2 and/or CYP2C9*3 alleles or VKORC1 AA genotype.
PO, IV (Children ⬎1 mo): Initial loading dose— 0.2 mg/kg (maximum dose: 10
mg) for 2– 4 days then adjust daily dose by results of INR, use 0.1 mg/kg if liver dysfunction is present. Maintenance dose range— 0.05– 0.34 mg/kg/day.
CAPITALS indicate life-threatening, underlines indicate most frequent.
Strikethrough ⫽ Discontinued.
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Implementation
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● High Alert: Medication errors involving anticoagulants have resulted in serious
NURSING IMPLICATIONS
Assessment
● Assess for signs of bleeding and hemorrhage (bleeding gums; nose●
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bleed; unusual bruising; tarry, black stools; hematuria; fall in hematocrit or BP; guaiac-positive stools, urine, or nasogastric aspirate).
Assess for evidence of additional or increased thrombosis. Symptoms depend on
area of involvement.
Geri: Patients over 60 yr exhibit greater than expected PT/INR response. Monitor
for side effects at lower therapeutic ranges.
Pedi: Achieving and maintaining therapeutic PT/INR ranges may be more difficult
in pediatric patients. Assess PT/INR levels more frequently.
Lab Test Considerations: Monitor PT, INR and other clotting factors frequently during therapy. Therapeutic PT ranges 1.3– 1.5 times greater than control; however, the INR, a standardized system that provides a common basis for
communicating and interpreting PT results, is usually referenced. Normal INR
(not on anticoagulants) is 0.8– 1.2. An INR of 2.5– 3.5 is recommended for patients at very high risk of embolization (for example, patients with mitral valve replacement and ventricular hypertrophy). Lower levels are acceptable when risk is
lower. Heparin may affect the PT/INR; draw blood for PT/INR in patients receiving
both heparin and warfarin at least 5 hr after the IV bolus dose, 4 hr after cessation
of IV infusion, or 24 hr after subcut heparin injection. Asian patients and those
who carry the CYP2C9*2 allele and/or the CYP2C9*3 allele, or those with VKORC1
AA genotype may require more frequent monitoring and lower doses.
Monitor hepatic function and CBC before and periodically throughout therapy.
Monitor stool and urine for occult blood before and periodically during
therapy.
Toxicity and Overdose: Withholding 1 or more doses of warfarin is usually
sufficient if INR is excessively elevated or if minor bleeding occurs. If overdose occurs or anticoagulation needs to be immediately reversed, the antidote is vitamin K
(phytonadione, AquaMEPHYTON). Administration of whole blood or plasma also
may be required in severe bleeding because of the delayed onset of vitamin K.
Potential Nursing Diagnoses
Ineffective tissue perfusion (Indications)
Risk for injury (Side Effects)
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harm or death from internal or intracranial bleeding. Before administering, evaluate recent INR or PT results and have second practitioner independently check
original order.
Do not confuse Coumadin (warfarin) with Avandia (rosiglitazone) or
Cardura (doxazosin). Do not confuse Jantoven (warfarin) with Janumet
(sitagliptin/metformin) or Januvia (sitagliptin).
Because of the large number of medications capable of significantly altering warfarin’s effects, careful monitoring is recommended when new
agents are started or other agents are discontinued. Interactive potential should be evaluated for all new medications (Rx, OTC, and natural
products).
PO: Administer medication at same time each day. Medication requires 3– 5 days
to reach effective levels; usually begun while patient is still on heparin.
Do not interchange brands; potencies may not be equivalent.
IV Administration
● Direct IV: Reconstitute each 5-mg vial with 2.7 mL of sterile water for injection.
Reconstituted solution is stable for 4 hr at room temperature. Diluent: No further dilution needed before administration. Concentration: 2 mg/mL. Rate:
Administer over 1– 2 min.
● Y-Site Compatibility: amikacin, ascorbic acid, bivalrudin, cefazolin, ceftriaxone, dopamine, epinephrine, heparin, lidocaine, morphine, nitroglycerin, oxytocin, potassium chloride, ranitidine.
● Y-Site Incompatibility: aminophylline, ceftazidime, ciprofloxacin, dobutamine,
esmolol, gentamicin, labetalol, promazine.
Patient/Family Teaching
● Instruct patient to take medication as directed. Take missed doses as soon as re-
membered that day; do not double doses. Inform health care professional of
missed doses at time of checkup or lab tests. Inform patients that anticoagulant effect may persist for 2– 5 days following discontinuation. Advise patient to read
Medication Guide before starting therapy and with each Rx refill.
● Review foods high in vitamin K. Patient should have consistent limited intake of
these foods, as vitamin K is the antidote for warfarin, and alternating intake of
these foods will cause PT levels to fluctuate. Advise patient to avoid cranberry juice
or products during therapy.
䉷 2015 F.A. Davis Company
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warfarin
● Caution patient to avoid IM injections and activities leading to injury. Instruct pa-
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tient to use a soft toothbrush, not to floss, and to shave with an electric razor during warfarin therapy. Advise patient that venipunctures and injection sites require
application of pressure to prevent bleeding or hematoma formation.
Advise patient to report any symptoms of unusual bleeding or bruising
(bleeding gums; nosebleed; black, tarry stools; hematuria; excessive
menstrual flow) and pain, color, or temperature change to any area of
your body to health care professional immediately. Patients with a deficiency in protein C and/or S mediated anticoagulant response may be at greater
risk for tissue necrosis.
Instruct patient not to drink alcohol or take other Rx, OTC, or herbal
products, especially those containing aspirin or NSAIDs, or to start or
stop any new medications during warfarin therapy without advice of
health care professional.
Advise patient to notify health care professional if pregnancy is planned or suspected or if breast feeding.
Instruct patient to carry identification describing medication regimen at all times
and to inform all health care personnel caring for patient on anticoagulant therapy
before lab tests, treatment, or surgery.
Emphasize the importance of frequent lab tests to monitor coagulation
factors.
Evaluation/Desired Outcomes
● Prolonged PT (1.3– 2.0 times the control; may vary with indication) or INR of 2–
4.5 without signs of hemorrhage.
Why was this drug prescribed for your patient?
⫽ Canadian drug name.
⫽ Genetic Implication.
CAPITALS indicate life-threatening, underlines indicate most frequent.
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