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Diphenhydramine Hydrochloride vs Citrate: What's the difference?

Medically reviewed by C. Fookes, BPharm. Last updated on Sep 5, 2019.

Official Answer

by Drugs.com

Diphenhydramine is a sedating antihistamine. It is available in four different salts:

  • Diphenhydramine citrate
  • Diphenhydramine hydrochloride
  • Diphenhydramine methylbromide
  • Diphenhydramine salicylate.

Only diphenhydramine citrate and diphenhydramine hydrochloride are used commercially.

The different salts have different molecular weights (diphenhydramine hydrochloride: 291.8 g/mol, diphenhydramine citrate: 447.5 g/mol) and rates of dissolution and absorption characteristics. Therefore the dosage differs depending on the salt used.

Diphenhydramine is available by itself for allergy, hay fever, skin irritations and insomnia and in combination with other active ingredients when used to treat other conditions, such as coughs, colds, and pain relief.

The following oral dosages for adults are given by the manufacturers. Dosages for children vary depending on age or body weight: please consult with a pediatrician.

Allergic rhinitis

  • Diphenhydramine citrate: 38mg to 76mg up to every four to six hours as needed. Maximum 456 mg/day
  • Diphenhydramine hydrochloride: 25mg to 50 mg up to every four to six hours as needed. Maximum 300 mg/day.

Cold symptoms, itch (pruritus), or urticaria

  • Diphenhydramine citrate: 38mg to 76mg up to every four to six hours as needed. Maximum 456 mg/day
  • Diphenhydramine hydrochloride: 25mg to 50 mg up to every four to six hours as needed. Maximum 300 mg/day

Insomnia

  • Diphenhydramine citrate: 76mg once at bedtime. Maximum dose 75mg
  • Diphenhydramine hydrochloride: 50mg once at bedtime. Maximum dose 50mg

Motion sickness

  • Diphenhydramine hydrochloride: 25mg to 50mg up to three or four times a day as needed

Note that these dosages are for adults who are otherwise healthy and are on no interacting medicines. The dosage of diphenhydramine may need reducing in those with certain medical conditions or taking certain medicines. Diphenhydramine may not be suitable for some

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).

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