In vitro study of the interaction between quinolones and polyvalent cations.

The aim of the present study was to evaluate the influence of aluminium and iron on the in vitro dissolution kinetics of ciprofloxacin and ofloxacin as well as the usefulness of this type of in vitro data to predict modifications in in vivo absorption processes as a consequence of different factors, such as the widely documented in vivo interaction between quinolones and cations. Fitting of experimental data to different theoretical in vitro dissolution profiles was performed by non-linear regression methods and the statistical moments were calculated from raw experimental data. Analysis of residuals applied to dissolution curves as well as statistical comparison of the estimated parameters were carried out to evaluate the in vitro interaction. The results reveal significative modifications of the dissolution profiles of these quinolones as a consequence of the presence of cations, especially for Fe2+ which decreases 34.7% the maximum amount dissolved for ciprofloxacin and 29.1% for ofloxacin. Al3+ also produces a decrease of the total amount of quinolone dissolved although less relevant than Fe2+. Analysis of residuals proved to be the best statistical method to evaluate differences between whole dissolution profiles, at least under the experimental conditions used.