[Application of the Weibull function to the study of in vivo/in vitro correlation]

After transformation of concentration-time curves by integration, the Weibull function is calculated, producing an equation for a derived function representing the plasma (or salivary) kinetics. This model can be employed in the analysis of in vivo/in vitro correlations, since cumulated dissolution percentages can be directly expressed as Weibull functions. A method was developed for prediction of salivary kinetics from in vitro dissolution data and the in vivo kinetics of a solution of the drug. This method was applied to results obtained for slow release formulations of acetaminophen and theophylline administered by the oral route.