A nurse is caring for a client with Parkinson's disease. The client has been prescribed oral diphenhydramine. Which of the following therapeutic outcomes should the nurse expect to see following administration of this medication?

A. Delay in disease progression: Diphenhydramine is an antihistamine with anticholinergic properties; it does not alter the underlying neurodegenerative process of Parkinson’s disease. Disease progression continues despite symptomatic management. Neuroprotective therapies or disease-modifying strategies are separate from symptomatic treatments like diphenhydramine. B. Improved bladder function: Parkinson’s disease–related bladder dysfunction typically results from detrusor overactivity and impaired autonomic regulation. Diphenhydramine does not target these mechanisms and may actually worsen urinary retention due to its anticholinergic effects. Management of bladder symptoms requires specific interventions such as antimuscarinic agents. C. Relief of depression: Depression in Parkinson’s disease is commonly treated with antidepressants such as selective serotonin reuptake inhibitors or other pharmacologic and nonpharmacologic approaches. Diphenhydramine has no established efficacy in mood disorders and does not address the neurotransmitter imbalances underlying depression. D. Decreased tremors: Diphenhydramine’s anticholinergic activity helps reduce tremors and muscle rigidity in Parkinson’s disease by balancing acetylcholine and dopamine activity in the central nervous system. It is particularly useful for mild tremor management, especially in clients who cannot tolerate other anticholinergic medications.