Drug General Information (ID: DDIAONZEMP)
  Drug Name Azithromycin Drug Info Dicoumarol Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Macrolides Anticoagulants
  Structure

 Mechanism of Azithromycin-Dicoumarol Interaction (Severity Level: Moderate)
     Increased risk of bleeding Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Azithromycin Dicoumarol
      Mechanism Potentiate the hypoprothrombinemic effect of vitamin K antagonist Vitamin K antagonist
      Key Mechanism Factor 1
Factor Name Bleeding
Factor Description Patients may be at risk for bleeding when the outcome of a disease or disease treatment confounds the standard mechanisms for maintaining hemostasis. Signs or symptoms of abnormal bleeding include: bleeding that takes a long time to stop (including nosebleeds, bleeding gums, bleeding from cuts and abrasions, and menstrual bleeding); severe unexplained bruising, or bruising that becomes larger; blood in the urine or stool, etc.
      Mechanism Description
  • Increased risk of bleeding by the combination of Azithromycin and Dicoumarol 

Recommended Action
      Management Given the potential for clinically significant interaction in the occasional, susceptible patient, close monitoring is recommended if azithromycin is prescribed during warfarin therapy. The INR should be checked frequently and warfarin dosage adjusted accordingly, particularly following initiation or discontinuation of azithromycin therapy in patients who are stabilized on their anticoagulant regimen. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools. The same precaution may be applicable during therapy with other oral anticoagulants, although clinical data are lacking.

References
1 Beckey NP, Parra D, Colon A "Retrospective evaluation of a potential interaction between azithromycin and warfarin in patients stabilized on warfarin." Pharmacotherapy 20 (2000): 1055-9. [PMID: 10999497]
2 Product Information. Zithromax (azithromycin). Pfizer US Pharmaceuticals, New York, NY.
3 Williams D, Ponte CD "Warfarin-associated hypoprothrombinemia: an unusual presentation." Am J Health Syst Pharm 60 (2003): 274-8. [PMID: 12613238]