Long-term use of diphenhydramine

The review article in CMAJ by McMillan and colleagues concluded that there is a paucity of long-term safety and efficacy data for the use of non-benzodiazepine sedative-hypnotics such as diphenhydramine.1

A recently published prospective cohort study reveals a higher cumulative strong anticholinergic use is associated with an increased risk for dementia. 2 Anticholinergics include tricyclic antidepressants, bladder antimuscarinics and first generation antihistamines.

Harvard Health Blog brings attention to this study linking the common anticholinergic drug Benadryl to increased dementia risk.3

In addition to being a non-benzodiazepine sedative-hypnotic, Benadryl is also used as an antihistamine.

Benadryl may contain different antihistamines. In Vancouver, it is diphenhydramine; in London, United Kingdom, it is cetirizine; in Cophenhagen, Denmark, it is acrivastine.4^,5

Benadryl-containing diphenhydramine is available in a number of countries worldwide including the United States, Canada, Singapore, Taiwan, Italy, Hong Kong and others. However, diphenhydramine is a banned substance in Zambia.

Patients should check the ingredients instead of relying on the brand name. Caution should be exercised for long-term use of Benadryl (diphenhydramine), an antihistamine and a non-benzodiazepine sedative-hypnotic, because of the association of increased risk for dementia.