Does Benadryl Make Your Heart Race?
In our latest question and answer, the pharmacist discusses whether or not Benadryl, an over-the-counter antihistamine, can cause your heart to race.
I took Benadryl and feel like it has opposite effects on me. My heart pounds. Does Benadryl make your heart race?
Aug 07, 2022- Benadryl can increase your heart rate due to its anticholinergic effects, even when taken at recommended doses.
- In rare cases, Benadryl may cause paradoxical excitation with symptoms like restlessness, agitation, and increased heart rate, especially in children.
- If you experience a faster heart rate or palpitations after taking Benadryl, talk to your pharmacist or doctor about whether it could be the cause.
Answer
Yes, Benadryl can increase your heart rate (i.e. "make your heart race"), even at recommended doses. This is because Benadryl, a sedating "first-generation" antihistamine, has strong anticholinergic effects.
Common anticholinergic side effects include:
- Feeling hot or overheated
- Constipation
- Dry eyes
- Dry mouth
- Tachycardia (i.e. increased heart rate)
- Confusion
- Sedation
- Dry skin
- Flushing
It should be noted that cardiac side effects of Benadryl, such as increased heart rate, aren't all that common. Nevertheless, if your heart rate has increased after dosing with Benadryl, or you are having palpitations, it may be the culprit.
Benadryl Causing Excitation
In addition, Benadryl has been reported to rarely cause "paradoxical excitation" in some individuals. It appears to be more common in children as well as in cases of an overdose according to the prescribing information for the drug. Symptoms of this include:
- Restlessness
- Agitation
- Insomnia
- Muscle spasms
- Increased heart rate
The side effect of "excitation" is noted as paradoxical as Benadryl is more commonly associated with a feeling of sedation, which is why it is used as a sleep aid.
Lastly, it appears certain individuals are more susceptible to the "excitation" side effects of Benadryl than others. The theory is that some individuals have genetic variations that increase the metabolism of Benadryl, increasing concentrations of an excitatory metabolite.
Final Words
Thanks again for your question!
References & sources
Glossary — Terms in This Answer
- Antihistamine
- A medication that blocks histamine, a chemical in your body that causes allergy symptoms like itching and swelling.
- Anticholinergic effects
- Side effects that occur when a medication blocks a certain type of nerve signal in your body, often causing dry mouth, constipation, and increased heart rate.
- Tachycardia
- A medical term for an abnormally fast heart rate.
- Palpitations
- A fluttering, pounding, or racing sensation in your chest that you can feel or notice.
- Paradoxical excitation
- An unexpected reaction where a medication meant to calm you down actually causes restlessness and agitation instead.
- Sedation
- A state of drowsiness or reduced alertness caused by a medication.
- Metabolite
- A substance produced when your body breaks down and processes a medication.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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