A 52-year-old man with a background history of ethanol abuse and seizure disorder presents with a 2-day history of unsteady gait, double vision, and increasing falls. He has been taking his regular phenytoin as prescribed (400 mg daily). He is drowsy but oriented. Exam reveals a small abrasion to his left forehead, bilateral horizontal nystagmus, slurred speech, past pointing to both arms, and a wide-based unsteady and ataxic gait. He denies self-harm or overdose. He states that his local doctor recently commenced him on a tablet to help his depression but he cannot remember its name. He claims not to have had a drink for 2 weeks.