Dementia And Antihistamine Use: A recent study in the JAMA Internal Medicine (2015) found significant memory impairment in patients using 2 classes of drugs:
1. 1st generation antihistamine ie: diphenhydramine and hydroxyzine
2. Tricyclin andepressants-especially doxepin.
The study included approximately 3500 subjects age 65 or older who at the entry into the study had no dementia. These subjects were followed every 2 years for a 10 year period, using pharmacy data to determine the cumulative exposure to this type of drugs.
Cognitive impairment appeared to be cumulative and not reversible. Whether this in some way is mainly a reflection of older age of the study subjects ("leaky brain") is not known. It may well apply to much younger subjects (think children).
Diphenhydramine (generic) and hydroxyzine (prescription) are both
used for the relief of hives and rashes, as well as, other allergies. In addition, diphenhydramine is liberally used in several OTC sleep aids. Doxepin,although an antidepressant, is often used for relief of hives and itching. All of these drugs are sedating.
Recommendation: Limit the use of both diphenhydramine and hydroxyzine. A better alternative is 2nd generation non sedating antihistamine such as fexofenadine or loratidine.