Diphenhydramine (DPH) is an antihistamine medication mainly used to treat allergies. It can also be used for insomnia, symptoms of the common cold, tremor in parkinsonism, and nausea.



Diphenhydramine.

Clinical data
Bioavailability 40–60%
Protein binding 98–99%
Metabolism Liver (CYP2D6, others)
Elimination half-life Range: 2.4–13.5 h

Where is Benadryl metabolized in the body?

Diphenhydramine undergoes extensive first-pass metabolism, whereby 50–60% of ingested medication is metabolized by the liver before reaching the systemic circulation. Nearly all the available drug is metabolized by the liver within 24–48 hours, thus increasing risk for liver injury.

Is Benadryl absorbed in stomach?

Diphenhydramine is relatively well absorbed, and its plasma concentration is rapidly elevated after oral administration (Paton and Web- ster, 1985), although it is mostly ionized over the pH range in the gastrointestinal tract.

How does Benadryl work in the body?

This medication works by blocking a certain natural substance (histamine) that your body makes during an allergic reaction. Its drying effects on such symptoms as watery eyes and runny nose are caused by blocking another natural substance made by your body (acetylcholine).

Is Benadryl taken internally?

Oral BENADRYL® Allergy products are meant to be ingested (swallowed). They come in tablet and liquid gel, and temporarily relieve the symptoms of upper respiratory allergies. Topical BENADRYL® itch relief products are only to be applied directly to the skin.

Is Benadryl OK for liver?

Despite widespread use over many decades, diphenhydramine has not been linked to liver test abnormalities or to clinically apparent liver injury. The reason for its safety may relate its short half-life and limited duration of use. Likelihood score: E (unlikely to be a cause of clinically apparent liver injury).

Does Benadryl affect the kidneys?

Acute kidney injury (AKI) can be caused by a commonly used over-the-counter and prescription medication, diphenhydramine (Benadryl, McNeil). We do not usually think of this drug as a major source of renal impairment, but it can cause problems in some predisposed patients, including elderly populations.

How is Benadryl excreted?

Diphenhydramine hydrochloride is widely distributed throughout the body, including the CNS. A portion of the drug is excreted unchanged in the urine, while the rest is metabolized via the liver.

Can you throw up Benadryl?

An overdose of Benadryl may result in extreme drowsiness, blurred vision, increased heart rate, confusion, seizures – even coma. Other symptoms may include dry mouth, nausea, vomiting, unsteadiness, high blood pressure, and hallucinations.

How long is Benadryl in your system?

For the average healthy adult, elimination half-life ranges from 6.7 to 11.7 hours. So between 6 to 12 hours after taking Benadryl, half the drug will be eliminated from the body. Within two days, the drug will be completely gone from the body.

What if you get Benadryl in your mouth?

Swallowing it can result in people receiving dangerously large amounts of the active ingredient, diphenhydramine. This can result in serious adverse events, such as unconsciousness, hallucinations, and confusion (see Data Summary).

Is it OK to take Benadryl every night?

Is it safe to take diphenhydramine every night? You should not take diphenhydramine every night. While it may be helpful during limited periods of insomnia, your body will build up a tolerance for the medication over time, and it will no longer have the desired effect.

Is it OK to take Benadryl to sleep?

Although antihistamines like Benadryl will make you feel sleepy, they’re not a great choice when it comes to treating insomnia. Not only can they affect your sleep quality, but they’ll also become less effective very quickly, meaning you may not notice any benefits if you use them often.

Is Benadryl good for anxiety?

Advantages. One of the biggest advantages of using an OTC medication such as Benadryl to treat anxiety is that it is fast-acting and convenient. These qualities can be helpful if you need to reduce symptoms of mild anxiety quickly. Because Benadryl causes many people to feel drowsy, it can also help with sleep.

Can you take Benadryl if you have Covid?

BENADRYL® products are only indicated to treat allergy symptoms, they are not symptomatic treatments for infectious diseases such as COVID-19.

What is a paradoxical reaction to Benadryl?

When a medication has an effect that’s the opposite of what’s expected, it’s called a paradoxical effect. In some people, taking Benadryl can actually have a stimulant effect, which is called paradoxical excitation. People that experience this after taking Benadryl may report feeling: excitable.

What should you not take with Benadryl?

Benadryl may interact with other types of medication, which can heighten the side effects.



Examples of medications that may interact with Benadryl include:

  • antidepressants.
  • stomach ulcer medicine.
  • cough and cold medicine.
  • other antihistamines.
  • diazepam (Valium)
  • sedatives.


Can Benadryl cause anxiety attacks?

Antihistamines are known to cause extreme drowsiness; however, in certain people, they can cause insomnia, excitability, anxiety, restlessness, and a rapid heart rate.

Does Benadryl cause dementia?

The research to date has not definitively proven that Benadryl (as a specific individual medication) raises the risk of developing dementia. However, the class of medications Benadryl belongs to (anticholinergics) does appear to be associated with dementia.

Is long term Benadryl use harmful?

Benadryl and some other antihistamine drugs can sometimes cause decreased memory, confusion, and trouble thinking. These side effects are more common in seniors. In addition, taking Benadryl long term might increase the risk of dementia such as Alzheimer’s disease, especially in seniors.

What are the 9 common pills linked to Alzheimer’s?

An estimated 47 million people worldwide were living with dementia in 2015, while in the United States around 5.7 million people have Alzheimer dementia, according to the study. Anticholergenic drugs include, but are not limited to, Artane, Bentyl, Oxytrol, Neosol, Symax and Vesicare.

Why is Benadryl not recommended for over 65?

Benadryl (diphenhydramine) and hydroxyzine are common examples of anticholinergic medications that are not cleared as well from the system in older people. This can lead to confusion, dry mouth, and constipation.

What is the ingredient in Benadryl that causes dementia?

Diphenhydramine is also used for motion sickness and extrapyramidal symptoms in Parkinson’s disease patients. Potential harm to the brain: Long-term anticholinergic use has been associated with increased dementia risk; diphenhydramine can impair many cognitive functions including memory.

What is the safest antihistamine for seniors?

Loratadine, cetrizine, and fexofenadine all have excellent safety records. Their cardiovascular safety has been demonstrated in drug-interaction studies, elevated-dose studies, and clinical trials. These three antihistamines have also been shown safe in special populations, including pediatric and elderly patients.

What is the safest sleep aid for seniors?

In the elderly, nonbenzodiazepines such as zolpidem, eszopiclone, zaleplon, and ramelteon are safer and better tolerated than tricyclic antidepressants, antihistamines, and benzodiazepines. Pharmacotherapy should be recommended only after sleep hygiene is addressed, however.

What drug puts you to sleep instantly?

Types of prescription sleeping pills

Sleep medication Helps you fall asleep Helps you stay asleep
Triazolam (Halcion)
Zaleplon (Sonata)
Zolpidem (Ambien, Edluar, Intermezzo, Zolpimist)
Zolpidem extended release (Ambien CR)

How much sleep does a 70 year old need?

7-8 hours

Sleep Changes in Older Adults. Most healthy older adults aged 65 or older need 7-8 hours of sleep each night to feel rested and alert. But as you age, your sleep patterns may change. These changes can cause insomnia, or trouble sleeping.