Comparison between in vitro dissolution and in vivo absorption of a new form of delayed-action theophylline
Brazier, J.L.; Comet, F.; Bannier, A.; Gillet, A.; Georges, D.
Annales Pharmaceutiques Francaises 43(1): 55-60
1985
ISSN/ISBN: 0003-4509 PMID: 4062182 Document Number: 263595
A study of comparing in vitro dissolution rate and in vivo absorption rate of a new sustained-release theophylline preparation is described. In vitro dissolution rate has been measured according to two procedures. In the first one, the pH of the dissolution medium was varied betwen 1.3 and 7.5 within 7 hours. These measurements show that dissolution is pH-independent and corresopnd to a zero order kinetics with a constant rate of 13.25% h-1. Absorption rate measured in vivo in six healthy volunteers shows that resorption corresponds to a zero order kinetics with a rate constant of 13.75% of the Cpmax. h-1. The comparison between these two parameters shows an excellent correlation. Such a pH-independent, zero order dissolution kinetics affords a constant individual absorption and very low interindividual variations in theophylline plasma levels during chronic treatment.