Jagadeeswaran Appusamy

Pharmacokinetic Principles The process of absorption, distribution, metabolism and excretion are often quantitated retrospectively so that dosage regimens that target therapeutic concentrations can be propectively predicted. The pharmacokinetic characteristics of a particular drug (rates of absorption, distribution, biotransformation, and excretion) determine its concentration in the plasma. Because the intensity of the tissue response is usually determined by the concentration of the drug in the direct environment of the receptors, a drug’s concentration in plasma is generally assumed to be correlated with the time course of its action. Dosage regimens are derived from pharmacokinetic studies in normal animals but often require modification in diseased, young, old, obese, thin, or pregnant animals. A large number of pharmacokinetic measures can be determined from time-course studies of drug concentrations in plasma, but only the more clinically useful features and values a

Pharmacokinetics Pharmacokinetics is the quantitative study of drug movement in, through and out of the body. Pharmacokinetics deals with the movement of drugs. A drug that is administered must be absorbed, distributed, metabolized and excreted. Pharmacokinetics deals with absorption, distribution, metabolism and excretion of drugs. In simple words it is described as what the body does to the drug. The intensity of response is related to concentration of the drug at the site of action, which in turn is dependent on its pharmacokinetic properties. Pharmacokinetic considerations, therefore, determine the route of administration, dose, latency of onset, time of peak action, duration of action and frequency of administration. Pharmacokinetic information is helpful in determining and adjusting the drug dosage schedules and in interpreting drug concentration data. A drug that is administered must move through different parts of the body and for this movement it must pass through vari