Download Drugs and Food Interactions Which Increase The Effects Of Warfarin

Drugs and Food Interactions Which Increase The Effects Of Warfarin
Highly Probable
Probable
Alcohol (if concomitant liver disease),
amiodorone, anabolic steroids, cimetidine,
clofibrate, cotrimoxazole, erythromycin,
fluconazole, isoniazid (600mg/d),
metronidazole, miconazole, omeprazole,
phenylbutazone, piroxicam*, propafenone,
propranolol, sulfinpyrazone ( biphasic with
later inhibition)
Possible
Acetaminophen, chloral hydrate,
ciprofloxacin, dextropropoxphene,
disulfiram, itraconazole, quinidine, phenytoin
(biphasic with later inhibition), tamoxifen,
tetracycline, flu vaccine
Acetylsalicylic acid, disopyramide,
fluorouracil, ifosfamide, ketoprofen,
lovastatin, metozalone, moricizine, nalidixic
acid, norfloxacin, ofloxacin, propoxyphene,
sulindac, tolmentin, topical salicylates,
cefamandole, cefazolin, gemfibrozil, heparin,
indomethacin, sulfisoxazole
*NSAIDS with no effect include: ketoralac, naproxen and ibuprofen
Drug and Food Interactions Which Decrease the Effects Of Warfarin
Highly Probable
Probable
Barbiturates, carbamazepine, chlordiazepoxide, cholestyramine,
griseofulvin, nafcillin, rifampin, sucralafate, high vitamin K content
foods, enteral feeds, large amounts of avocado
Dicloxacillin
Possible
Azathiprine, cyclosporine,
etretinate, trazodone
Overdosage/Toxicity Guidelines
INR
Greater than the therapeutic
level but < 5.0
Patient Situation
Action
and
No significant
bleeding
Lower the dose or omit a dose and resume therapy at a lower dose when the
INR is at a therapeutic level. *
> 5.0 but < 9.0
and
No significant
bleeding
Omit the next one or two doses, monitor the INR more frequently, and
resume therapy at a lower dose when the INR is at therapeutic level.
Alternatively, omit the dose and administer vitamin K, 1 to 2.5 mg orally,
particularly if the patient is at increased risk of bleeding. If more rapid
reversal is required because the patient requires urgent surgery, administer
vitamin k, 2 to 4 mg orally, with the expectation that a reduction of the INR
will occur in 24 h. if the INR is still high, administer an additional dose of
vitamin K, 1 to 2 mg orally (all grade C compared with no treatment).
>9
and
No significant
bleeding
Hold off on warfarin therapy and administer a higher dose of vitamin K, 3
to 5 mg orally, with the expectation that the INR will be reduced
substantially in 24 to 48 h. Monitor the INR more frequently and administer
additional vitamin K if necessary. Resume therapy at a lower dose when the
INR reaches the therapeutic level (all grade 2C compared with no
treatment).
with
Serious bleeding
Hold off on warfarin therapy and administer vitamin K, 10 mg by slow IV
infusion, supplemented with fresh frozen plasma or prothrombin complex
concentrate depending on the urgency of the situation. Administration of
vitamin K can be repeated every 12 h ( grade 2C).
> 20
*If the INR is only minimally greater than the therapeutic range, no dose reduction may be required ( grade 2C)
For patients with life- threatening bleeding, hold off on warfarin therapy and administer prothrombin complex concentrate
supplemented with vitamin K, 10mg by slow IV infusion. Repeat this treatment as necessary, depending on the INR (grade 2C).
Available Tablet Strengths And Colors Of Coumadin
Strength
1 mg
2 mg
2.5 mg
3 mg
4 mg
5 mg
6mg
7.5 mg
10 mg
Color
Pink
Lavender
Green
Brown
Blue
Peach
Teal
Yellow
White
References:
1. Hirsh J, Dalen JE, Anderson DR, et al. Oral anticoagulants:
mechanism of action, clinical effectiveness, and optimal
therapeutic range. Chest 2001: 119; 8S-21S.
2. Ansell J, Dalen, JE, Anderson D, Deykin D. Managing Oral
Anticoagulant Therapy. Chest 2001: 119; 22S-38S.
Updated by: Keith T. Veltri, R.Ph., Pharm D. Candidate, St.. John’s
University College of Pharmacy 2001
Warfarin (Coumadin) Flow Sheet
Patient Name:
Rm #:
Date of Birth:
Indication:
Duration:
Target INR:
Start Date:
Expected D/C Date:
Recommended Therapeutic Range for Oral Anticoagulant Therapy
Indications:
INR:
Prophylaxis of venous thrombosis (high-risk surgery)
2.0-3.0
Treatment of venous thrombosis
Duration of Therapy
Treatment of PE
12 mos-life :
Prevention of systemic embolism
Tissue heart valves
AMI (to prevent systemic embolism) *
Valvular heart disease
AF
Mechanical prosthetic valves (high risk)
Bileaflet mechanical valve in aortic position
2.0-3.0
3-6 months: First event with reversible or timelimited risk factor
 6 month : Idiopathic VTE, first event
First event with:
Cancer, until resolved
Anticardiolipin antibody
Antithrombin deficiency
Recurrent event, idiopathic or with
thrombophelia
2.5-3.5
2.0-3.0
*if oral anticoagulant therapy is elected to prevent recurrent MI, an INR of 2.5 to 3.5 is recommended, consistent with US Food and Drug
Administration recommendations.
DATE:
CURRENT DOSE:
INR:
NEW DOSE:
COMMENTS: