Does Benadryl Make Your Heart Race?

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

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