Over-the-Counter Medications

Publication Date: 
Wed, 04/01/2015
By: Alere Staff

Over-the-counter medications (OTC) are available for nearly every ailment and can be found at most stores open 24 hours a day. New OTC medications and improvements to OTC formulas are being created all the time and can be available without a prescription. However, easy to get and non-prescription strength doesn’t mean they are safe for you, particularly if you are a patient on warfarin and are unsure of drug interactions.

As a patient on warfarin, it is possible to develop unwanted drug interactions while taking OTC medications.1 OTC 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 changes with INR results.2 For example, medications for pain, in many cases, still include aspirin which can increase the risk of bleeding even in patients not taking warfarin. Also, antacids still do not include cautionary use for patients taking warfarin that a decrease in an INR test may result.1

For this reason, it’s important to tell your doctor about all OTC medications you are taking or wish to take. Ask your doctor for a list of approved OTC medications and products for colds, fever, allergies, cough, arthritis, and pain relief. You can use this list when shopping for your OTC products. To help you create this list, we have developed a tool you can use to make sure your choice will be a safe one. Download the Safe Medication List here. You can also find it under the Tools for Anticoagulation Patients page on this website.


  1. Bristol-Myers Squibb Company. (October 2011). Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb 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.