<prompt> Therapeutic Index is:ED50LD50LD50ED50ED50-LD50ED50 XLD50  <response>: ref; KD Tripathi Pharmacology 7th edition page no:55 The gap between the therapeutic effect DRC Dose Response Curveand the adverse effect DRC defines the safety margin or the therapeutic index of a drug. Therapeutic index median lethal dose median effective dose or LD 50 ED 50 