This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacodynamics, Subject name: Pharmacology
[{'content': 'Which drug has wide therapeutic index \nSelect and explain. \nA. Digoxin, B. Lithium, C. Phenytoin, D. Penicillin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is \'d\' i.e., Penicillin The therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinic desired or effective response in population of individuals. Therapeutic index = (Toxic dose) / (Effective dose) The therapeutic index is thus a measure of the drug\'s safety, since a large value indicates that there is wide margin between doses that are effective and that are toxic."Phenytoin has narrow therapeutic index" page 372, 5th/e K.D.T."Lithium has narrow therapeutic index" page 416, 5th/e K.D.T."Digitalis has narrow therapeutic index" page 462, 5th/e K.D.T.', 'role': 'assistant'}]