This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
[{'content': 'Which of the following is not used to treat ADHD? \nSelect and explain. \nA. Dexamphetamine, B. Dexmethylphenidate, C. Dextromethorphan, D. Clonidine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Dextromethorphan is a NMDA antagonist used as cough suppressant.', 'role': 'assistant'}]