Warfarin & Antibiotics Interactions

• Drug interactions with warfarin therapy are a common and significant cause of morbidity and mortality and should be considered whenever starting or stopping a drug (particularly antibiotics).
  

• In general, dose adjustments should only be made after checking the INR at 48-72 hours after initiating an interacting medication.
  

• The INR should continue to be monitored every 48-72 hours for the course of interacting medication therapy or until INR is again confirmed stable.
  

• Red: ++ The interaction may be life-threatening and/or require medical intervention to minimise or prevent serious adverse effects; or the drugs are contraindicated for concurrent use.
• Black: + The interaction may result in an exacerbation of the patient’s condition and/or require an alteration in therapy.
  

Reference :

1. https://www.health.qld.gov.au/publications/clinical-practice/guidelines-procedures/medicines/warfarin-guidelines.pdf