A 63-year-old man has been experiencing increasing confusion and agitation for the past 4 hours. His symptoms started with a headache earlier in the day, then he became very anxious and started pacing around the house. He has a history of depression and a recent back injury at work last week. His current medications are tramadol and fluoxetine. His temperature is 102°F, heart rate is 115 bpm, respirations are 20/minute, and blood pressure is 160/100 mm Hg. He appears anxious and diaphoretic. He knows his name but is unable to tell you where he is and what time it is. Physical exam reveals dilated pupils and muscle rigidity. Deep tendon reflexes are 3 bilaterally in all extremities. Which of the following is the most likely diagnosis? Anticholinergic toxicity Neuroleptic malignant syndrome Opioid overdose Serotonin syndrome