ABSTRACT
To achieve an optimal drug response from a dosage form, a drug should be delivered to its site of action at a concentration that both minimizes its side effects and maximizes its therapeutic effects. The drug concentration at its target site depends on the dose of the drug administered, and the rate and extent of its absorption, distribution, metabolism, and elimination (ADME/pharmacokinetics). For a drug molecule to exert its biological effect, it must be absorbed unaltered in signicant quantity (absorption), be transported by the body –uids, escape widespread distribution to unwanted tissues, traverse the biological membrane barriers, penetrate in adequate concentration to the sites of action (distribution), escape metabolism and excretion (metabolism and elimination), and interact with its target in a specic fashion to cause the desired alteration of cellular function (pharmacodynamics).
