Correlation of ‘in vitro’ release and ‘in vivo’ absorption characteristics of four salbutamol sulphate formulations

The purpose of this study was to investigate the possibility to develop different levels of correlation between ‘in vitro’ dissolution parameters and ‘in vivo’ pharmacokinetic parameters for four salbutamol sulphate formulations: two commercially available formulations (Ventolin® Oral and Volmax®) and two sustained-release formulations (SG7 and SG14) developed in our laboratory. A level A correlation of ‘in vitro’ release and ‘in vivo’ absorption could be set up for individual plasma level data by means of the deconvolution method. Linear correlations could be obtained when dose fraction released ‘in vitro’ was plotted vs. dose fraction absorbed ‘in vivo’, with correlation coefficients between 0.97 and 0.99 for the formulations studied. A second level of correlation between mean ‘in vitro’ dissolution time (MDT) and mean ‘in vivo’ residence time (MRT) was performed with a correlation coefficient of 0.81. Finally, it was also possible to establish a good ‘in vitro’-‘in vivo’ correlation when the mean dissolution time ‘in vitro’ and Tmax or Cmax ‘in vivo’ were compared, but it appeared impossible to establish any correlation between mean dissolution time (MDT) and AUC.