A nurse is assessing a client who takes citalopram to treat depression. Which of the following findings should the nurse identify as an indication of serotonin syndrome?

Choice A reason: Constipation is not a hallmark symptom of serotonin syndrome. It may occur with certain medications but does not reflect the hyperactivity of the serotonergic system seen in serotonin syndrome. Choice B reason: Muscle flaccidity is inconsistent with serotonin syndrome, which typically presents with neuromuscular hyperactivity such as rigidity, tremors, or clonus. Choice C reason: Lethargy may be present in many conditions but is not a defining feature of serotonin syndrome. The syndrome often includes agitation, confusion, and hyperreflexia rather than sedation. Choice D reason: Tremors are a classic sign of serotonin syndrome, reflecting neuromuscular excitation. Other signs include hyperreflexia, clonus, fever, and autonomic instability. Prompt recognition is critical to prevent progression to life-threatening complications.