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
Narrow therapeutic index is seen with: 
Select and explain. 
A. Desipramine, B. Lithium, C. Penicillin, D. Diazepam
B: Lithium
Answer: B: Lithium 
Explanation: Ans. B. LithiumDrugs with narrow therapeutic Index: digoxin, theophylline, lidocaine, cyclosporine, clonidine, anticonvulsant (Phenytoin), TCA (imipramine), aminoglycosides, glipizide (not metformin)