This paper describes the main development steps of pharmacokinetics that paralleled the development of
analytical bioassay methods. From the first stirrings on 1950s, with very sensitive but not specific radiotracing
measurements using 14C or 3H labelled drugs, to further developments with more specific methods like gas chromatography,
high pressure liquid chromatography, to the last achievement with tandem mass spectrometry, pharmacokinetics
has supported all the development procedures of both NDA (New Drug Application) and ANDA (Abridged New Drug
The discovery of new therapeutic active molecules is now concentrated in a few very big companies, and requires
pharmacokinetic support from the first screening procedures to the last clinical developments.
Medium and small pharmaceutical companies largely use pharmacokinetics for various new applications of existing
drugs now out of patent, that require only or mainly pharmacokinetic, bioavailability, bioequivalence investigations in
compliance with the ANDA procedure.
In spite of guidelines published by US FDA and EU EMA, some open problems on bioequivalence would still require
more attention from regulatory authorities, like how to manage the puzzle of endogenous substances, ethical problems
against the repeated-dose regimen with some drugs and how to manage Cmax in the presence of the multiple-peak