[Bioavailability of drugs--concepts and problems]

The development of the concept of bioavailability is dealt with on the basis of definitions published in the literature. In this connexion, the often extent divergency between the definition and the determination of bioavailability in practice is indicated. Furthermore, the bioavailability is differentiated from the amount of absorption. With regard to the inclusion of the levels of in vitro liberation, liberation in the body and absorption achieved, the frequently stated use of one and the same term for different contents gives rise to a disentanglement of the terms. Perspectively, the inclusion of animal experimentation in pharmacokinetic-biopharmaceutical investigations is insisted on.