Which drug has wide therapeutic index

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.