[Comparative in vitro and in vivo study of several long-acting theophyllines]

This study describes the comparative in vitro and in vivo release of six slow-release formulations. In vitro, with half-change method, differences appear in the profiles, some formulations showing a linear release (Dilatrane, Euphylline LA, Théostat), the others an irregular release with 'plateau' related to the pH gradient (Armophylline, Cétraphylline, Théolair). In vivo, at steady state, the fluctuations are less important and the comparative kinetic study in ten normal healthy volunteers after chronic oral dosing of six different formulations show a slight variability in the theophylline release during 12 h. Great interindividual variations appear with all formulations. In fact, none of the formulations present an ideal release over a 12 h period.