Diphenhydramine

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Two bright pink diphenhydramine tablets (generic form of Benadryl)

Diphenhydramine or diphenhydramine hydrochloride is a commonly used antihistamine, which is also used for coughs, to aid sleep, for certain symptoms of Parkinson's diease, as well as for allergy symptoms, bites, itching and eczema.[1][2] Diphenhydramine is the active ingredient in Benadryl, which is sometimes used as a sleep aid as well as an anti-histamine.[1]

Additional active ingredients[edit | edit source]

Products containing diphenhydramine often contain other ingredients, for example:

Other common ingredients include:

  • ethyl (a form of alcohol) especially in cough syrups
  • food colorings, especially reds and blues[3]

Brand names[edit | edit source]

Diphenhydramine is marketed under many different brand names including:

  • Allermax
  • Banophen
  • Benadryl
  • Benylin Chesty Coughs Original and Benylin Mucus Cough Nights (syrup)
  • Compoz Nighttime Sleep Aid
  • Covonia Nighttime Forumla
  • Diphedryl or Diphenhis
  • Nytol One-A-Night
  • Nytol QuickCaps
  • QlearQuil Nightitme Allergy Relief
  • Siladryl Allergy
  • Silphen Cough
  • Sominex original
  • Tranquil
  • Twilite
  • Vanamine PD
  • Unisom Sleepgels maximum strength
  • Z-Sleep
  • ZzzQuil[1][5][6]

Theory[edit | edit source]

Evidence[edit | edit source]

Dosage[edit | edit source]

The usual dose suggested is:

  • creams for bites, itches or eczema - apply a thin layer once or twice a day
  • allergies and hayfever, itching or as an anti-histamine - 25mg to 25mg, 3 or 4 times a day
  • cough and cold symptoms – diphenhydramine is typically mixed with other medicines, the dose depends on the medicine
  • creams for bites, itches or eczema - apply a thin layer once or twice a day
  • sleep problems or insomnia - 25mg to 50mg[2]

Risks and safety[edit | edit source]

Diphenhydramine has a wide range of side effects include dizziness and drowsiness.[1]

It is described as non-addictive/not habit forming, but recently concerns have been raised about long term use including the reduced effectiveness in the long term, causing people to increase the dose.[7] Theoharides and Stewart (2016) stated that in high risk over 65s taking 50mg for 3 years or 50mg for 3 years was associated with cognitive dysfunction.[7]

Using a product containing diphenhydramine marketed for nighttime pain, coughs or cold and flu also involves the side effects of other active ingredients, or from inactive ingredients such as food colorings.[3][6]

Costs and availability[edit | edit source]

Diphenhydramine is available over the counter, under many different brand names including Benadryl.[1] Diphenhydramine is available in tablet, capsule or syrup/liquid form, and in anti-histamine products as a cream, spray or ointment to be applied to the skin.[8]

In the UK, diphenhydramine is a pharmacy-only medication and is not given on prescription.[3] Diphenhydramine is available under the brand names Benylin Chesty Coughs, Histergan, and Nytol Once-A-Day.[2]

See also[edit | edit source]

Learn more[edit | edit source]

References[edit | edit source]

  1. 1.01.11.21.31.4 "Diphenhydramine Uses, Dosage & Side Effects". Drugs.com. Retrieved November 9, 2020.
  2. 2.02.12.2 "Diphenhydramine (including Nytol Original & Histergan): drowsy antihistamine". National Health Service. September 21, 2018. Retrieved February 14, 2021.
  3. 3.03.13.23.33.4 "Electronic Medicines Compendium". www.medicines.org.uk. Retrieved February 13, 2021.
  4. "Levomenthol". Drugs.com. Retrieved February 13, 2021.
  5. "£8.59 - Benylin Chesty Coughs Original 300ml". Weldricks Pharmacy. Retrieved February 12, 2021.
  6. 6.06.1 "Covonia Night Time Formula - Summary of Product Characteristics (SmPC)". www.medicines.org.uk. Retrieved February 13, 2021.
  7. 7.07.1 Theoharides, TC; Stewart, JM (2016). "Antihistamine and mental status" (PDF). J Clin Psychopharmacol. 36 (3): 195–7.
  8. "Diphenhydramine Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing". www.webmd.com. Retrieved February 13, 2021.

expectorant An antitussive is a cough suppressant, an expectorant is a cough suppressant that helps someone discharge or cough up mucus.

adverse reaction Any unintended or unwanted response to a treatment, whether in a clinical trial or licensed treatment. May be minor or serious.

The information provided at this site is not intended to diagnose or treat any illness.
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