A client with schizophrenia is prescribed risperidone. The nurse observes muscle stiffness and a shuffling gait. What is the most likely cause of these symptoms?

Choice A reason: Serotonin syndrome involves fever, agitation, and hyperreflexia due to excessive serotonin, typically from SSRIs or MAOIs, not antipsychotics like risperidone. Muscle stiffness and shuffling gait are not characteristic, making this an incorrect cause of the symptoms. Choice B reason: Neuroleptic malignant syndrome causes severe muscle rigidity, fever, and autonomic instability due to dopamine blockade by antipsychotics. While possible with risperidone, the client’s mild symptoms (stiffness, shuffling gait) are more consistent with extrapyramidal effects than this severe condition. Choice C reason: Extrapyramidal symptoms, caused by risperidone’s dopamine D2 receptor blockade, include muscle stiffness and shuffling gait (parkinsonism). These occur due to disrupted basal ganglia function, mimicking Parkinson’s disease, and are common with antipsychotics, making this the most likely cause. Choice D reason: Tardive dyskinesia involves involuntary movements like grimacing or lip smacking, typically after long-term antipsychotic use. Muscle stiffness and shuffling gait are not characteristic, as these are parkinsonian symptoms, making this less likely than extrapyramidal symptoms.