Warfarin drug interactions

 

 

Drug Interaction Classification Systems
Significance Rating (A) Criteria   Management Rating (B) Criteria
0 Not listed   0 Not listed
1 Severity - Major: The effects are potentially life-threatening or capable of causing permanent damage.
Documentation: interaction is suspected, probable or established
  1 Avoid combination
2 Severity - Moderate: The effects may cause deterioration in a patient's clinical status. Additional treatment, hospitalization, or an extended hospital stay may be necessary.
Documentation: interaction is suspected, probable or established
  2 Usually avoid combination
3 Severity - Minimal: The effects are usually mild; consequences may be bothersome or unnoticeable but should not significantly affect the therapeutic outcome. Additional treatment is usually not required.
Documentation: interaction is suspected, probable or established
  3 Minimize risk
4 Severity – Major or Moderate
Documentation: Interaction is possible
  4 No action needed
5 Severity: Minor
Documention: possible
OR
Severity: Major, Moderate or Minor
Documentation: interaction is unlikely
  5 No interaction
A. Tatro DS (ed). Drug Interaction Facts. St Louis MO: Wolters Kluwer, 2010
B. Hansten P,Horn J. Drug Interactions Analysis and Management. St Louis MO: Wolters Kluwer 2010.

 

 

 

Drug/Drug Class Effect on INR Proposed Mechanism Significance (A) Management (B)
acarbose increased Unexplained Mechanisms 4 0
acetaminophen increased Inhibition of Warfarin Metabolism 2 3
alcohol (acute use) increased Inhibition of Warfarin Metabolism 4 3
alcohol (chronic use) decreased Induction of Warfarin Metabolism 4 3
allopurinol increased Inhibition of Warfarin Metabolism 4 3
aminoglutethamide decreased Induction of Warfarin Metabolism 2 3
amiodarone increased Inhibition of Warfarin Metabolism 1 3
amitriptyline increased Inhibition of Warfarin Metabolism 0 4
Androgens increased Unexplained Mechanisms 1 2
aprepitant decreased Induction of Warfarin Metabolism 4 3
ascorbic acid decreased Unexplained Mechanisms 5 3
aspirin/salicylates no effect Increased Bleeding Risk 1 2
azathioprine decreased Unexplained Mechanisms 2 3
azithromycin increased Inhibition of Warfarin Metabolism 1 5
Azole Antifungals increased Inhibition of Warfarin Metabolism 1 3
Barbiturates decreased Induction of Warfarin Metabolism 1 2
bosentan decreased Induction of Warfarin Metabolism 2 3
capecitabine increased Inhibition of Warfarin Metabolism 1 3
carbamazepine decreased Induction of Warfarin Metabolism 2 3
carboplatin increased Unexplained Mechanisms 1 0
celecoxib increased Inhibition of Warfarin Metabolism 1 4
Cephalosporins increased Decreased Synthesis of Clotting Factors 2 2
chloral hydrate increased Protein Binding Displacement 3 3
chloramphenicol increased Inhibition of Warfarin Metabolism 2 0
cholestyramine decreased Reduced Absorption of Warfarin 2 3
cimetidine increased Inhibition of Warfarin Metabolism 1 2
ciprofloxacin increased Inhibition of Warfarin Metabolism 1 3
clarithromycin increased Inhibition of Warfarin Metabolism 1 3
clofibrate increased Unexplained Mechanisms 1 2
clopidogrel/ticlopidine no effect Increased Bleeding Risk 0 4
colestipol decreased Reduced Absorption of Warfarin 2 3
Contraceptives, Oral decreased Increased Clotting Factor Synthesis/Activity   0 2
Corticosteroids either Unexplained Mechanisms 2 4
cyclophosphamide increased Unexplained Mechanisms 1 3
cyclosporin decreased Unexplained Mechanisms 4 4
delavirdine increased Inhibition of Warfarin Metabolism 4 0
diazoxide increased Protein Binding Displacement 0 4
dicloxacillin decreased Induction of Warfarin Metabolism 2 4
diltiazem  increased Unexplained Mechanisms 0 4
Direct Thrombin Inh. increased Additive Anticoagulant Response 2 0
disopyramide increased Unexplained Mechanisms 5 4
disulfiram increased Inhibition of Warfarin Metabolism 2 2
efavirenz increased Inhibition of Warfarin Metabolism 4 0
erythromycin increased Inhibition of Warfarin Metabolism 1 3
ethacrynic acid increased Protein Binding Displacement 4 4
ethcholvynol decreased Induction of Warfarin Metabolism 2 3
etoposide increased Unexplained Mechanisms 1 0
felbamate increased Unexplained Mechanisms 4 4
fenofibrate increased Unexplained Mechanisms 1 3
fluorouracil increased Inhibition of Warfarin Metabolism 1 3
fosphenytoina either Induction or Inhibition of Warfarin Metabolism 2 3
gefitinib increased Unexplained Mechanisms 2 0
gemcitabine increased Unexplained Mechanisms 1 3
gemfibrozil increased Unexplained Mechanisms 1 2
glutethamide decreased Induction of Warfarin Metabolism 2 2
glyburide increased Unexplained Mechanisms 0 3
griseofulvin decreased Induction of Warfarin Metabolism 2 3
heparin/LMWHs increased Additive Anticoagulant Response 0 3
ifosfamide increased Inhibition of Warfarin Metabolism 4 0
influenza vaccine increased Unexplained Mechanisms 4 4
isoniazide increased Inhibition of Warfarin Metabolism 4 3
isotretinoin increased Unexplained Mechanisms 4 4
leflunamide increased Inhibition of Warfarin Metabolism 4 0
levofloxacin increased Inhibition of Warfarin Metabolism 1 4
lovastatin  increased Inhibition of Warfarin Metabolism 1 3
mefloquine increased Unexplained Mechanisms 4 3
menthol decreased Unexplained Mechanisms 4 4
mercaptopurine decreased Unexplained Mechanisms 2 3
mesalamine increased Unexplained Mechanisms 4 3
methimazole decreased Reduced Catabolism of Clotting Factors 1 3
metronidazole increased Inhibition of Warfarin Metabolism 1 2
mineral oil increased Unexplained Mechanisms 5 4
mitotane decreased Induction of Warfarin Metabolism 4 3
moxifloxacin increased Inhibition of Warfarin Metabolism 1 0
nafcillin decreased Induction of Warfarin Metabolism 2 3
nalidixic acid  increased Inhibition of Warfarin Metabolism 2 3
neomycin increased Impaired Vitamin K Production by Gut Flora 5 3
norfloxacin increased Inhibition of Warfarin Metabolism 1 3
NSAIDs no effect Increased Bleeding Risk 1 2
ofloxacin increased Inhibition of Warfarin Metabolism 1 3
omeprazole increased Inhibition of Warfarin Metabolism 4 4
orlistat increased Inhibition of Warfarin Metabolism 4 4
paclitaxel increased Unexplained Mechanisms 1 0
phenytoina decreased Induction or Inhibition of Warfarin Metabolism 2 3
prasugrel no effect Increased Bleeding Risk 0 0
primidone decreased Induction of Warfarin Metabolism 1 2
progestins increased Unexplained Mechanisms 4 4
propafenone increased Inhibition of Warfarin Metabolism 4 3
propoxyphene  increased Unexplained Mechanisms 4 3
propranolol   increased Unexplained Mechanisms 4 4
propylthiouracil decreased Reduced Catabolism of Clotting Factors 1 3
Protease Inhibitors decreased Unexplained Mechanisms 4 3
quinidine increased Inhibition of Warfarin Metabolism 1 3
quinine increased Inhibition of Warfarin Metabolism 1 0
reserpine increased Unexplained Mechanisms 0 4
ribavirin decreased Unexplained Mechanisms 4 3
Rifamycins decreased Induction of Warfarin Metabolism 2 2
rofecoxib increased Inhibition of Warfarin Metabolism 1 4
simethicone decreased Reduced Absorption of Warfarin 0 4
simvastatin increased Inhibition of Warfarin Metabolism 1 4
spironolactone decreased Hemoconcentration of Clotting Factors  5 4
SSRIs increased Inhibition of Warfarin Metabolism 4 3
sucralfate decreased Reduced Absorption of Warfarin 5 3
Sulfa Antibiotics increased Inhibition of Warfarin Metabolism 1 3
Sulfinpyrazone increased Inhibition of Warfarin Metabolism 1 2
tamoxifen increased Unexplained Mechanisms 4 0
telithromycin increased Inhibition of Warfarin Metabolism 1 4
temafloxacin increased Inhibition of Warfarin Metabolism 1 4
terbinafine decreased Induction of Warfarin Metabolism 4 0
testosterone increased Unexplained Mechanisms 4 0
Tetracyclines increased Impaired Vitamin K Production by Gut Flora 1 3
Thiazide Diuretics decreased Hemoconcentration of Clotting Factors  5 4
Thrombolytics increased Additive Anticoagulant Response 1 0
Thyroid Hormones increased Increased Catabolism of Clotting Factors 1 3
tolterodine increased Unexplained Mechanisms 4 4
tramadol increased Unexplained Mechanisms 2 0
trazodone decreased Unexplained Mechanisms 2 4
trastuzumab increased Unexplained Mechanisms 4 0
vitamin E increased Decreased Synthesis of Clotting Factors 1 3
vitamin K decreased Increased Clotting Factor Synthesis/Activity   2 3
zafirlukast increased Inhibition of Warfarin Metabolism 0 3