This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Pharmacology, Subject name: Pharmacology
[{'content': 'Therapeutic drug monitoring is required in all except: \nSelect and explain. \nA. Phenytoin, B. Metformin, C. Tacrolimus, D. Cyclosporine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (B) Metformin(Ref: KDT 8th/e p42)* We can easily monitor blood glucose levels as an effect of metformin, thus TDM is not required.* TDM is required for lithium, digitalis, phenytoin, immunosuppressants and anti-arrhythmics, etc.', 'role': 'assistant'}]