This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
[{'content': 'Narrow therapeutic index is seen with: \nSelect and explain. \nA. Desipramine, B. Lithium, C. Penicillin, D. Diazepam', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. LithiumDrugs with narrow therapeutic Index: digoxin, theophylline, lidocaine, cyclosporine, clonidine, anticonvulsant (Phenytoin), TCA (imipramine), aminoglycosides, glipizide (not metformin)', 'role': 'assistant'}]