Variation in drug responsiveness to a paicular dose of the drug in different individuals can be obtained from

* Drug response to the same drug used in same doses in a population varies based on many factors governing pharmacodynamic variability (like age, genetics, co- morbid condition, concomitant medication, etc) operant in that subset of population under study. * This pharmacodynamic variability in a population is analyzed using a Quantal Dose Response Curve * Quantal Dose Response relationship is an "all or none" plot traced based on response elicited to varying dose of drug administered to a population. * Therapeutic Index of a drug is determined based on data plots from Quantal Dose Response Curves. * Median Effective Dose (ED50) is the dose of a drug required to produce a specified effect in 50% of the population. * In preclinical studies, the Median Lethal Dose (LD50) is determined in experimental animals - the dose that produced moality of 50% of animal group used in testing. * Therapeutic Index is determined as a ratio of LD50/ED50 - provides the safety margin of a drug. The wider the Lethal DRC is spaced away from the Therapeutic effect DRC --> Drug has a wide safety margin. Ref:- Goodman & Gilman's Pharmacological basis of Therapeutics 13th Ed; Pg Num:- 36