The document discusses the importance of pharmacokinetic parameters in drug therapy. It describes key parameters like volume of distribution, clearance, half-life, and how they can be used to determine dosing regimens. Volume of distribution relates the amount of drug in the body to its concentration in blood. Clearance predicts the rate of drug elimination based on its concentration. Half-life is the time for the drug amount in the body to reduce by half. These parameters along with target concentration can be used to calculate loading and maintenance doses to achieve a rational dosage regimen. Disease states can impact pharmacokinetic parameters by altering clearance, volume of distribution and half-life.