Therapeutic index is a measure of

(c) Safety,Ref: Lippincott, 6th ed., pg. 35The therapeutic index (TI) of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response in a population of individuals:TI=TD50/ED50Where TD50 = the drug dose that produces a toxic effect in 50% the population and ED50 = the drug dose that produces a therapeutic or desired response in 50% the population. TI is a measure of a drug's safety, because a larger value indicates a wide margin between doses that are effective and doses that are toxic.