system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 43-year-old man is brought to the physician for a follow-up examination. He has a history of epilepsy that has been treated with a stable dose of phenytoin for 15 years. He was recently seen by another physician who added a drug to his medications, but he cannot recall the name. Shortly after, he started noticing occasional double vision. Physical examination shows slight vertical nystagmus and gait ataxia. Which of the following drugs was most likely added to this patient's medication regimen?
assistant
Cimetidine