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What is the max dose of diphenhydramine for adults?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Oct 4, 2021.

I took two 50mg capsules thinking they were 25mg each (that is I took 100mg instead of 50mg) and it was the only thing that put me into a nice 6 hour sleep which I have not had for weeks! If it is acceptable I will try to take this to finally get some good sleep!

Official Answer

by Drugs.com

The maximum oral dose of diphenhydramine for adults is generally reported as 100mg for a single dose or no more than 300mg in 24 hours, but this can vary depending on what condition diphenhydramine is being used for, the salt of diphenhydramine used (there are two salts available in the United States, diphenhydramine citrate and diphenhydramine chloride), the age of the person, how much diphenhydramine they have tolerated before, and if they are on any interacting medications. Taking too much diphenhydramine can be fatal.

Diphenhydramine is one of the most abused medications in the United States and a 2016 study found that diphenhydramine overdosage accounted for 3.2% of all overdosage deaths in the United States and ranked among the top 15 drugs most frequently involved in drug overdose deaths in the United States. Most diphenhydramine intoxication/overdose cases occur in children ages 6 years or younger. Children who have taken or been given more than 7.5mg/kg of diphenhydramine should be taken to a healthcare facility for observation because they require medical supervision and management. Diphenhydramine overdose or intoxication can be either accidental or intentional.

What is the maximum dose of diphenhydramine for sleep?

When used as a sleep aid the maximum recommended dosage is 76mg for diphenhydramine citrate or 50mg for diphenhydramine hydrochloride. Although diphenhydramine is commonly used for sleeping it is not recommended because it prevents the brain from achieving restorative deep REM sleep and tends to cause anxiety or a “hangover” effect, which causes a person to feel drowsy the next day. Alternatives, such as zolpidem, are preferred as a sleep aid.

Taking diphenhydramine as a sleep aid for more than 7 to 10 nights is not recommended, because you will gain tolerance to it.
Diphenhydramine should never be given to children to help them sleep and is best not given to children younger than 12 years of age without the direction of a physician. Use in children under 6 years old should be avoided. Long-acting tablets or capsules should never be given to children.

What are the symptoms of diphenhydramine overdose or toxicity?

Diphenhydramine can be harmful in large amounts. Symptoms of a diphenhydramine overdose include:

  • Blurred vision
  • Confusion
  • Dry mouth
  • Dry skin
  • Drowsiness
  • Hallucinations (seeing or hearing things that aren't there)
  • Heart rhythm disturbances such as QT prolongation
  • Nausea and/or vomiting
  • Nervousness
  • Psychosis
  • Seizures
  • Sleepiness
  • Tremor
  • Unsteadiness.

Recovery from a diphenhydramine overdose is likely if the person survives the first 24 hours but in some people, serious heart rhythm disturbances may occur, which can cause death.

What medicines contain diphenhydramine?

Diphenhydramine may be found in many medicines, sometimes in combination with other ingredients such as acetaminophen or ibuprofen, for example:

  • Advil PM
  • Aleve PM
  • Bayer PM
  • Benadryl
  • Dimetapp
  • Ivarest
  • Nytol
  • Sominex
  • Tylenol PM
  • Unisom.

What brands contain diphenhydramine hydrochloride and diphenhydramine citrate?

Common brands containing diphenhydramine and the salt they contain include:

  • Advil PM (diphenhydramine citrate)
  • Aleve PM (diphenhydramine hydrochloride)
  • Bayer PM (diphenhydramine citrate)
  • Benadryl (diphenhydramine hydrochloride)
  • Dimetapp (diphenhydramine hydrochloride)
  • Ivarest (diphenhydramine hydrochloride)
  • Sominex (diphenhydramine hydrochloride)
  • Tylenol PM (diphenhydramine hydrochloride)
  • Unisom (diphenhydramine hydrochloride).


References
  • Diphenhydramine overdose Mt Sinai.https://www.mountsinai.org/health-library/poison/diphenhydramine-overdose
  • Huynh DA, Abbas M, Dabaja A. Diphenhydramine Toxicity. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557578/
  • Zhang D, Tashiro M, Shibuya K, Okamura N, Funaki Y, Yoshikawa T, Kato M, Yanai K. Next-day residual sedative effect after nighttime administration of an over-the-counter antihistamine sleep aid, diphenhydramine, measured by positron emission tomography. J Clin Psychopharmacol. 2010 Dec;30(6):694-701. doi: 10.1097/jcp.0b013e3181fa8526. PMID: 21105284.
  • Katayose Y, Aritake S, Kitamura S, Enomoto M, Hida A, Takahashi K, Mishima K. Carryover effect on next-day sleepiness and psychomotor performance of nighttime administered antihistaminic drugs: a randomized controlled trial. Hum Psychopharmacol. 2012 Jul;27(4):428-36. doi: 10.1002/hup.2244. PMID: 22806823.

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