The difference between diphenhydramine hydrochloride and diphenhydramine citrate is that the salt used to bind the diphenhydramine, is different. For diphenhydramine hydrochloride the salt is hydrochloride and for diphenhydramine citrate the salt is citrate. This salt can change how quickly and effectively the diphenhydramine dissolves and is absorbed but once it is in the body it has no effect. Essentially 25 mg of diphenhydramine hydrochloride is equivalent to 38 mg of diphenhydramine citrate.
Diphenhydramine is actually 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.
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 4-6 six hours as needed. Maximum 456 mg/day
- Diphenhydramine hydrochloride: 25mg to 50 mg up to every 4-6 six hours as needed. Maximum 300 mg/day.
Cold symptoms, itch (pruritus), or urticaria
- Diphenhydramine citrate: 38mg to 76mg up to every 4-6 six hours as needed. Maximum 456 mg/day
- Diphenhydramine hydrochloride: 25mg to 50 mg up to every 4-6 six hours as needed. Maximum 300 mg/day
Insomnia
- Diphenhydramine citrate: 76mg once at bedtime. Maximum dose 76mg
- Diphenhydramine hydrochloride: 50mg once at bedtime. Maximum dose 50mg
Motion sickness
- Diphenhydramine hydrochloride: 25mg to 50mg up to 3 to 4 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).