Is There An Interaction Between Warfarin With Benadryl?

In our latest question and answer, the pharmacist discusses taking Benadryl with warfarin.


Does Benadryl have any interactions with someone taking warfarin?

Asked by Cathy On Aug 24, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Aug 24, 2022
Last updated Sep 29, 2023

Key points

  • Warfarin has no known drug interaction with Benadryl (diphenhydramine).
  • Always ask your doctor or pharmacist before combining warfarin and over-the-counter medications to avoid potentially dangerous drug interactions.


There is no known interaction between Benadryl (diphenhydramine) and warfarin. They are considered safe to take together.

In fact, as it concerns over-the-counter allergy medication, most are safe to take with warfarin since they don't interact with it and don't affect blood coagulation on their own.

OTC Warfarin Interactions

Even though warfarin doesn't interact with OTC allergy medications, there are some drugs you need to be cautious with that you can get without a prescription. It is always a good idea to look into potential drug interactions, even with over-the-counter drugs, if you are taking a blood thinner like warfarin.

Not only do some drugs have blood thinning properties on their own (like NSAIDs), many are known to either increase or decrease warfarin concentrations in the blood which can significantly alter its effects.

If warfarin concentrations are increased via a drug interaction, there is an increased risk of serious bleeds.

If warfarin concentrations are decreased via a drug interaction, it may not be as effective, putting you at risk for blood clots.

There are several over-the-counter medications that you need to be aware of if you take warfarin, including:

  • Aspirin
  • Ibuprofen
  • Naproxen
  • St. John's Wort
  • Red years rice
  • Pepto-Bismol (Bismuth Subsalicylate)
  • Pepcid
  • Prilosec
  • Zantac

Fortunately, as mentioned, OTC allergy medications are not known to interact with warfarin. All of the following should be safe to take with it:

  • Claritin (loratadine)
  • Allegra (fexofenadine)
  • Zyrtec (cetirizine)
  • Benadryl (diphenhydramine)
  • Xyzal (levocetirizine)
  • Chlor-Trimeton (chlorpheniramine)

Final Words

If you are suffering from allergies and looking for an allergy medication for relief, you can feel safe taking them with warfarin.

Which allergy medication you choose to take should depend on what you are looking for.

Second-generation antihistamines (like Allegra and Claritin) are non-drowsy and last around 24 hours per dose. They are a good option for all-day allergy relief.

If you are looking for something sedating, Benadryl and Chlor-Trimeton would be options and can help you fall asleep at night.


  • Prescribing Warfarin Appropriately to Meet Patient Safety Goals., PubMed
  • Drug interactions with warfarin: what clinicians need to know, PubMed
  • Warfarin Monograph, PubChem

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at! You can also connect with Dr. Brian Staiger on LinkedIn.

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