Can Benadryl Make You Hyper?

Answer

Benadryl (diphenhydramine) is a commonly used antihistamine for the treatment and prevention of allergies. In addition, due to its sedating properties, it is used before bedtime to help combat insomnia and induce drowsiness.

Somewhat surprisingly, Benadryl can have the opposite effect in some individuals and cause CNS (central nervous system) stimulation, even at recommended dosages. This is sometimes known as paradoxical excitation.

Some describe this reaction as making them feel "hyper" or anxious  Studies indicate that this occurs most commonly in children and adolescents but has been reported in adults as well.

Benadryl Causes CNS Stimulation In Some Individuals

Symptoms of paradoxical CNS stimulation include:

• Restlessness
• Agitation
• Muscle Spams
• Insomnia
• Nervousness
• Irritability
• Seizures (rare)

The incidence of CNS excitation with Benadryl use isn't known and the mechanism behind it isn't well understood either.

One possible theory involves individuals who have a genetic variation that causes multiple copies of a metabolizing enzyme known as CYP2D6. These individuals are known as "ultra-rapid metabolizers".  It is thought that Benadryl may be quickly converted to a compound (due to extensive metabolism) that causes excitation.

How Long Can These Side Effects Last?

Whatever the cause, CNS stimulation doesn't tend to last longer than the usual duration of action of Benadryl, about four to six hours. Occasionally, the effects may last slightly longer due to longer-lasting metabolites.

Studies indicate the half-life (i.e., the time it takes for 50% of the drug to be metabolized) of Benadryl and associated metabolites is 2-8 hours and is completely eliminated within 24-48 hours. Therefore, your side effects shouldn't continue for more than one or two days.

Final Words

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