Can The Effects Of Benadryl Last Into The Next Day?

Answer

Benadryl (diphenhydramine) is a commonly used over-the-counter treatment for insomnia due to its sedative effects. While somewhat effective in decreasing sleep latency (i.e. time it takes to fall asleep), it hasn't been found to be very effective for increasing total sleep time and is associated with a variety of side effects such as:

• Dry mouth
• Dry eyes
• Constipation
• Next day grogginess
• Dizziness
• Next day sedation

Benadryl (Diphenhydramine) Next Day Drowsiness

For most individuals, after taking it by mouth, the sedative effects of Benadryl will begin to occur in 20-45 minutes. Peak sedative effects are reported to occur around 1 to 2 hours after dosing.

The usual duration of action of Benadryl is 4 to 6 hours but this can be greatly increased in older adults.

Benadryl use, especially in the elderly, has been associated with next-day grogginess. This is sometimes known as a "hangover" effect or "Benadryl hangover".

Although Benadryl generally only lasts 4 to 6 hours for most individuals, a variety of studies, such as this one, have reported next-day grogginess and hangover effects in many individuals.

Some studies have gone as far as to verify that Benadryl (diphenhydramine) is still bound to receptors in the brain the next morning after nighttime dosing in certain individuals, which could lead to sedative effects.

Age Is A Big Factor In Benadryl Metabolism

Most data indicates that as we age, the metabolism of many drugs, including Benadryl slows down.

For example, one study found that the half-life (i.e. time it takes for 50% of a drug to be metabolized) of Benadryl is nearly tripled in the elderly when compared to children. Specifically, the study found the half-life of Benadryl to be the following in different age groups:

• Children: ~5.5 hours

• Young Adults: ~9.2 hours

• Elderly: ~13.5 hours

Genetic differences in individuals can also be a significant factor in how quickly individuals metabolize medication.

If you do feel next day grogginess or a "hangover" feeling on Benadryl, know that the effects are not uncommon. In most cases, the effects should dissipate throughout the day and should not last more than a day or two.

Benadryl (Diphenhydramine) Sleep Recommendations

Most guidelines, such as those from the American Academy Sleep Medicine, don't recommend using Benadryl for insomnia due to insufficient evidence for benefits and the potential side effects. 

If you have been using Benadryl and have had problems with next-day drowsiness, speak with your doctor regarding possible alternatives.

Final Words

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