The significance of pharmacodynamic measurements in the assessment of bioavailability and bioequivalence of psychotropic drugs using CEEG and dynamic brain mapping.

There are a variety of problems in evaluating the bioavailability of psychotropic drugs. Psychotropics have many metabolites; there are discrepancies between peripheral plasma levels and therapeutic effects, and psychotropics must penetrate the blood-brain barrier to have an effect on their target organ. Therefore, "classical" pharmacokinetic evaluation may not be sufficient to determine the bioavailability and bioequivalence of these drugs. Additional and more precise information may be obtained by adding pharmacodynamic procedures to these evaluations. Quantitative pharmaco-EEG (QPEEG), which uses the computer-analyzed electroencephalogram (CEEG), may be the method of choice for determining the pharmacodynamic profiles of psychotropic drugs at the central nervous system (CNS) level. The difficulties in evaluating the bioavailability of psychotropics, as well as the results of several studies that confirm the significance of CEEG as a pharmacodynamic measure, are discussed.