Hematology and Oncology Book

Tranfusion

http://www.fpnotebook.com/

Warfarin Drug Interactions

Aka: Warfarin Drug Interactions, Drug Interactions with Coumadin, Coumadin Drug Interactions
  1. See Also
    1. Coumadin (Warfarin)
    2. Coumadin Protocol
    3. Coumadin Protocol for the Perioperative Period
  2. Risk Factors: Drug Interaction with Warfarin
    1. Older age
    2. Acutely ill
    3. Dietary change
    4. Concurrent infection
  3. Precautions
    1. Avoid using agents with major Drug Interactions with Warfarin
    2. When using medications known to affect INR, monitor INR closely
      1. Check INR 5 days after starting medication
      2. Check INR after stopping the medication
  4. Drug Interactions: Agents that increase INR or bleeding risk
    1. Acetaminophen (Tylenol)
    2. Alcohol
    3. Amiodarone (Cordarone)
      1. Adjustment per Amiodarone maintenance dose
        1. Amiodarone 400 mg/day: Reduce Warfarin dose 40%
        2. Amiodarone 300 mg/day: Reduce Warfarin dose 35%
        3. Amiodarone 200 mg/day: Reduce Warfarin dose 30%
        4. Amiodarone 100 mg/day: Reduce Warfarin dose 25%
      2. Reference
        1. Sanoski (2002) Chest 121:19-23 [PubMed]
    4. Anabolic Steroids
    5. Antifungal Medications
      1. Fluconazole (Diflucan)
      2. Ketoconazole (Nizoral)
      3. Itraconazole (Sporanox)
      4. Miconazole (Monistat)
    6. Aspirin and Salicylates
    7. Cephalosporins
      1. Cefoperazone (Cefobid)
      2. Cefamandole (Mandol)
      3. Cefotetan (Cefotan)
      4. Cefmetazole (Zefazone)
    8. Chloral Hydrate
    9. Cimetidine (Tagamet)
    10. Clofibrate
    11. Cranberry Juice (CYP2C9 inhibitor)
      1. Appears safe in at least one clinical trial
      2. Greenblatt (2006) Clin Pharmacol Ther 79:125-33 [PubMed]
    12. Danazol (Danocrine)
    13. Diflunisal (Dolobid)
    14. Disulfiram (Antabuse)
    15. Ginkgo Biloba (independent effect due to antiplatelet activity)
    16. Heparin
    17. HMG CoA Reductase inhibitors
    18. Isoniazid (INH)
    19. Macrolides
      1. Erythromycin
      2. Clarithromycin
    20. Metronidazole (Flagyl)
      1. High risk Drug Interaction (can significantly increase INR with bleeding risk 2-4 fold over baseline)
      2. Avoid if possible and if not, consider decreasing Septra dose by 25-40%
    21. Nalidixic Acid
    22. NSAIDs
    23. Omeprazole (Prilosec)
    24. Paroxetine (Paxil)
    25. Penicillin
    26. Propafenone (Rythmol)
    27. Quinidine
    28. Quinolones
    29. Selective Serotonin Reuptake Inhibitors (SSRI) and Serotonin Norepinephrine Reuptake Inhibitors (SNRI)
      1. Fluvoxamine (Luvox)
      2. Fluoxetine (Prozac)
      3. One additional patient on Warfarin for Atrial Fibrillation with SNRI or SSRI will have have a major bleeding event
        1. (2014) Presc Lett 21(11): 65
        2. Sansone (2009) Psychiatry 6(7): 24–29 [PubMed]
    30. Sulfinpyrazone (Anturane)
    31. Tamoxifen
    32. Tetracycline
    33. Thyroid Hormone (Thyroxine or Synthroid)
    34. Ticlopidine (Ticlid)
    35. Trimethoprim-Sulfamethoxazole (Bactrim, Septra)
      1. High risk Drug Interaction (can significantly increase INR with bleeding risk 2-4 fold over baseline)
      2. Avoid if possible and if not, consider decreasing Septra dose by 25-40%
    36. Vitamin E
      1. Theoretical bleeding risk, but appears to be safe in clinical trials
      2. Dereska (2006) J Surg Res 132:121-9 [PubMed]
  5. Drug Interactions: Drugs that decrease INR or increase clotting risk
    1. American Ginseng (no effect on Warfarin with Asian Ginseng)
    2. Barbiturates
    3. Binding Resins
    4. Carbamazepine (Tegretol)
    5. Oral Contraceptives
    6. Penicillin
    7. Rifampin
      1. Avoid if possible and if not, consider increasing Warfarin dose by 25-40%
    8. St. John's Wort
    9. Vitamin K
  6. Drug Interactions: Drugs that have a variable effect on INR or bleeding risk
    1. Allopurinol
    2. Corticosteroids
    3. Phenytoin (Dilantin)
  7. Drug Interactions: Lowest risk antibiotics for interaction
    1. Amoxicillin
    2. Azithromycin
    3. Cepahlosporins
  8. References
    1. Horton (1999) Am Fam Physician [PubMed]
    2. Gage (2000) Am J Med 109:484 [PubMed]

You are currently viewing the original 'fpnotebook.com\legacy' version of this website. Internet Explorer 8.0 and older will automatically be redirected to this legacy version.

If you are using a modern web browser, you may instead navigate to the newer desktop version of fpnotebook. Another, mobile version is also available which should function on both newer and older web browsers.

Please Contact Me as you run across problems with any of these versions on the website.

Navigation Tree