A nurse is caring for a client with schizophrenia who has been receiving haloperidol for the past 10 days. The client becomes increasingly restless, frequently shifting in their chair, and states. "I feel like I need to keep moving, but I don't know why." Vitals are stable, and no distress is reported aside from the restlessness. Which of the following actions should the nurse take first?

Rationale: A. Reassurance alone does not address the underlying cause of the restlessness, which may be distressing and impair functioning. B. Although this can be an expected side effect (akathisia), documenting without intervention neglects the client's discomfort. C. Notifying the provider is important, but immediate symptom relief is the priority before adjusting long-term therapy. D. The client is exhibiting signs of akathisia, a common extrapyramidal side effect of haloperidol. Diphenhydramine (an anticholinergic/antihistamine) can relieve symptoms promptly and should be administered as the first nursing action.