NCLEX Yellow Book Klimek’s Version (KV) Practice Test

Diphenhydramine, an antihistamine, is known for its anticholinergic properties, which can lead to a range of adverse effects, particularly in the elderly population. These properties can cause issues such as dry mouth, constipation, urinary retention, blurred vision, and confusion. In older adults, who may already be experiencing age-related changes in their physiological response, the use of anticholinergic medications can exacerbate these issues, leading to significant risk of falls, cognitive impairment, and other complications.

The elderly are often more susceptible to the side effects of anticholinergic drugs because they may have comorbid conditions, take multiple medications that also have anticholinergic effects, or already have diminished organ function. Therefore, the presence of these properties in diphenhydramine poses a significant risk for this population, making it contraindicated.

While cardiovascular risks, respiratory depression, and neurological effects are valid concerns with many medications, the prominence of anticholinergic effects particularly highlights the dangers specific to the aging population, reinforcing why this property specifically is particularly crucial in assessing the safety of diphenhydramine for elderly patients.