A client with Parkinson's disease is taking diphenhydramine 25 mg by mouth three times daily. Which outcome should the nurse expect?

• A. Delay in disease progression
• B. Improved bladder function
• C. Relief of depression
• D. Decreased tremors

Answer: (D)

In Parkinsonian tremor, there is an imbalance in the brain where acetylcholine activity becomes relatively high because dopamine-producing neurons are diminished. Anticholinergic effects help rebalance this by blocking acetylcholine, which can lessen tremor and rigidity. Diphenhydramine, though primarily an antihistamine, has anticholinergic properties and can reduce tremors associated with Parkinson’s disease. So, the expected outcome is a decrease in tremors.

This won’t slow disease progression, and it isn’t expected to improve bladder function or treat depression. Anticholinergic effects can cause dry mouth, constipation, urinary retention, blurred vision, and confusion, especially in older adults.