Basics of PK-PD using QEEG: acute/repetitive administration, interactions. Focus on anxiolytics with different...

Utilizing computer-assisted quantitative analysis of the electroencephalogram (EEG) in combination with certain statistical procedures and under specific design conditions, it is possible to objectively evaluate the functional bioavailability of psychotropic substances in the target organ: the human brain. Specifically, one may determine whether a drug is active in the central nervous system (CNS) compared with placebo in humans, the dose effect (including nonmonotonic drug effects along the continuum range of concentrations) and the time effect (including time-dependent pharmacodynamic phenomena as tolerance and sensitization), as well as its activity in relation to the formulation and route of application. Methodological aspects are introduced, discussing the usefulness of evaluating different treatments, doses, time points, states, target variables, electrodes and even different groups. Several issues are raised in relation to acute vs. repetitive administration, particularly those dealing with statistical comparisons when making conclusions about acute, repetitive or superimposed effects, and in relation to human psychotropic interactions, such as mechanistic drug-drug interaction descriptions, drug metabolites and enantiomers, as well as the importance of acquiring drug plasma concentrations, elapse of time and topographic distributions to accurately identify its occurrence. PK-PD modeling is introduced as a tool to enlarge the scope of inferences that can be derived when using pharmaco-EEG. The examples presented in order to develop the arguments are mainly focused on anxiolytic compounds belonging to the different neurochemical groups, benzodiazepines and azaspirones. Questions that have yet to been resolved are also addressed.