Over-the-Counter Medications

When taking warfarin, sometimes taking over-the-counter (OTC) medicines can have an unwanted drug interaction.1 It is important to keep your INR, or International Normalized Ratio, within a safe therapeutic range.

Over-the-counter product interactions can result in low or high INR test results and may cause serious complications. Warfarin is among the leading medications involved in drug interactions, resulting in either a high or low INR.2 For this reason, it’s important to tell your doctor about all over-the-counter medication you are taking or wish to take.

By law, prescription medications must be accompanied by an informational sheet to inform patients about the medication, possible side effects and caution against other medication use that might cause an unwanted interaction.

Ask your doctor for a list of approved over-the-counter medications and products for colds, fever, allergies, cough, arthritis, and pain relief. You can use this list when shopping for your over-the-counter products.

  1. Bristol-Myers Squibb Company. (2007). Medication Guide for Coumadin Tablets and Coumadin for Injection. Princeton, NJ: Bristol-Myers Squibb Pharma Company.
  2. Newman, D. (2006). The prevalence of non-therapeutic and dangerous international normalized ratios among patients receiving warfarin in the emergency department. American College of Emergency Physicians, 48, 182-189.