A nurse is caring for an elderly patient who has been taking diphenhydramine (Benadryl) for insomnia. Which central nervous system effect is the nurse most likely to observe in this patient?

A. No CNS effects, diphenhydramine doesn't cross the blood brain barrier.: Diphenhydramine readily crosses the blood-brain barrier, which is why it causes central nervous system effects such as sedation. B. Diphenhydramine is known to cause seizures in elderly clients: Seizures are not a typical side effect of diphenhydramine. While high doses may lower seizure threshold in rare cases, confusion and sedation are far more common CNS effects in older adults. C. Diphenhydramine can cause confusion and sedation in an elderly client: Elderly patients are particularly sensitive to anticholinergic effects of diphenhydramine, leading to sedation, dizziness, and confusion. These CNS effects can increase fall risk and impair cognitive function, making careful monitoring essential. D. Diphenhydramine can cause euphoria in an elderly client: Euphoria is not a standard effect of diphenhydramine. The drug primarily causes sedation and anticholinergic side effects rather than mood elevation in older adults.