Some examples for the possibilities and limitations of pharmacoelectroencephalography as a method in clinical pharmacology.

Pharmacoelectroencephalography is a new methodology using clinical pharmacological research designs and the method of electroencephalography, and its parametrisation by computer analysis. Pharmacoelectroencephalography is considered to be the most sensitive method for describing drug effects on the human CNS on a functional electrophysiological level. There is an unrevoked hypothesis that all drugs effecting the CNS do reflect those effects in well designed, well conducted and well analysed pharmacoelectroencephalographical studies. On the other hand, if a systematic pharmacoelectroencephalographical study does not verify an effect, then, according to this hypothesis, the drug does not have functional effects on the CNS. The EEG however, is not a direct indicator of toxic effects on the central nervous system. Therefore, from lack of pharmacoelectroencephalographical effects it cannot be concluded that a drug has no toxic effects on the CNS. Pharmacoelectroencephalography has been used to show the efficacy of drugs on a functional CNS level, to establish dose- and time relationships of CNS active drugs, and to suggest dosage levels for therapeutic use and time intervals for their application. Furthermore, with pharmacoelectroencephalography a drug's influence on vigilance and vigilance regulation can be described, and substances can - within certain limits - be screened for their eventual psychotropic properties. It will be demonstrated that pharmacoelectroencephalography provides a sensitive and very useful method for clinical pharmacology, without which the development of new drugs is nowadays almost impossible. However, there are strict limitations for the use of this method and the interpretation of its results: The EEG is not sufficiently validated externally. It is an experimental model based on the electrical activity of the awake brain. The meaning of the changes in this activity is almost completely unknown. Although it has been possible to classify a high number of psychotropic drugs into a predetermined five drug class system on the basic of their EEG effects (19) and although certain drugs have been found whose psychotropic properties were predicted from the EEG (26), it is not possible to describe a drug's psychotropic properties by means of the EEG. The EEG indicates CNS effects, but not necessarily psychotropic properties, even though useful information can be obtained at very early stages in a drug's development, about its influence on vigilance and the organization of the brain's electrical activity.