Which first-generation antihistamine is listed as having strong anticholinergic properties?

• A. Diphenhydramine
• B. Loratadine
• C. Cetirizine
• D. Fexofenadine

Answer: (A)

In this topic, the concern is anticholinergic burden in older adults. First-generation antihistamines often cross into the brain and can produce strong anticholinergic effects (dry mouth, constipation, urinary retention, confusion, delirium), which Beers Criteria warns about for the elderly. Diphenhydramine is a classic example of a first-generation antihistamine with notable anticholinergic activity and high sedative potential, making it risky for older patients. The other drugs listed—loratadine, cetirizine, and fexofenadine—are second-generation antihistamines with minimal anticholinergic effects and less central nervous system penetration, so they do not carry the same level of risk in this regard.