Prilosec OTC® and Warfarin

Publication Date: 
Sun, 5/1/2016
By: Alere Staff


Suffering from stomach acid-related health issues is not fun for anyone. Stomach acid is a natural part of your digestive system, helping our body to digest the food we intake. Unfortunately, sometimes our bodies generate an excessive amount which can lead to issues like heartburn, stomach pain, GERD and possibly ulcers. If you are someone who suffers from these symptoms, then you understand the misery around it. Thankfully, there are treatment options that you and your doctor can try to figure out what is best for you. 

A proton pump inhibitor (PPI) is a new class of medication that may be considered for you. A commonly prescribed PPI is the Prilosec OTC® medication, also known by its generic name as omeprazole. It is available both by prescription as well as over-the-counter which makes it easily accessible.1

Interactions with Warfarin

When you are taking warfarin, sometimes there are interactions with other medications. You may wonder how the Prilosec OTC® medication may or may not interfere with your warfarin. The information available on interactions generally focuses around how your body metabolizes both medications and this can be confusing and difficult to understand. 

The interaction between the Prilosec OTC® medication and warfarin has received much attention, but there is not a clear answer as to whether or not it can interfere with your warfarin and INR results. One study hints that taking the Prilosec OTC® medication and warfarin together may increase your INR results, putting you at risk of bleeding.2 Another study states that that there is no special attention that is required and that a warfarin dosage adjustment is not needed.3 Despite not providing a clear answer, both studies did agree that the INR should be monitored closely for a few weeks if you start taking the Prilosec OTC® medication while taking warfarin. 

If you have been advised to start the Prilosec OTC® medication, it is best to contact the doctor or clinic that manages your warfarin. They will decide if you need to change your warfarin dose and also when you should have your INR tested again. 


  1. Harvard Health Letter. Proton-Pump Inhibitors. Harvard Health Publications. April 1, 2011. Retrieved from the website:
  2. Prilosec (Omeprazole) – Drug Interactions, Contraindications, Overdosage, etc.  Retrieved from the website:
  3. Shirayama, T., Shiraishi, H., Kuroyanagi, A., Hamaoka, T., Imai, M. and Kojima, A. Interaction between Warfarin and Proton Pump Inhibitors. International Journal of Clinical Medicine, 2014, 5, 836-843.

PRILOSEC OTC® is a registered trademark of Procter and Gamble Company. Alere is not affiliated or associated with Procter and Gamble Company or the PRILOSEC OTC® trademark.