Which antihistamine is considered inappropriate for use in older adults due to anticholinergic effects?

• A. Amlodipine
• B. Loratadine
• C. Cetirizine
• D. Diphenhydramine (oral)

Answer: (D)

The main idea here is the anticholinergic burden of medications in older adults and how Beers Criteria guides safer choices. Diphenhydramine is a first-generation antihistamine that strongly blocks acetylcholine at muscarinic receptors and penetrates the central nervous system easily. This combination leads to pronounced anticholinergic effects such as confusion, memory problems, delirium, dry mouth, constipation, urinary retention, and even increased fall risk. In older patients, these effects are especially problematic because they can worsen cognition and overall function, so diphenhydramine is considered inappropriate for routine use in this population.

In contrast, second-generation antihistamines like loratadine and cetirizine have little anticholinergic activity and limited CNS penetration, making them much safer choices for older adults. Amlodipine, while listed among the options, is not an antihistamine at all; it’s a calcium channel blocker used for blood pressure and chest pain, so it doesn’t carry the same anticholinergic risk in this context.