This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epilepsy, Subject name: Pharmacology
[{'content': 'High plasma drug concentration of phenytoin can cause which of the following adverse effects? \nSelect and explain. \nA. Ataxia, B. Hirsutism, C. Gum hyperplasia, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cerebellar dysfunction (ataxia, nystagmus and veigo) is seen at toxic plasma concentrations whereas hirsutism and gum hyperplasia is seen at therapeutic concentrations (but on prolonged use).', 'role': 'assistant'}]