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Combined dissolution and permeation systems are designed to simultaneously assess the dissolution of a pharmaceutical dosage form and the permeation of dissolved drugs therefrom. However, there were still some limitations on predicting the possible absorption rate-limiting steps and improving the in vitro-in vivo correlation (IVIVC) of a complete dosage form. In this study, the modified biorelevant media with some solubilizers and pH modifiers were integrated into the drug dissolution/absorption simulating system (DDASS). Indapamide, a poorly soluble compound (pKa = 8.8), was selected to validate the applicability of the modified biorelevant media. The elution and permeation dynamics of indapamide were investigated by using appropriate solubilizing agents in the DDASS. The absorption behaviors were analyzed after oral administration of indapamide in beagle dogs. The absorption rate-limiting steps and IVIVCs were predicted from the dissolution-permeation-absorption dynamic parameters. As a result, the absorption fraction of indapamide in the FaSSIFmod of DDASS was estimated to be approximately 100%, in accordance with its high permeability. The ratios of permeation rate to elution rate were 2.55 and 3.34 for the immediate- and sustained-release tablets of indapamide, respectively, suggesting a dissolution rate-limiting absorption for indapamine. In addition, point-to-point correlations were established between in vitro elution and in vivo absorption by the nonlinear and linear regression analysis ways (r > 0.85). The findings indicate that DDASS is a promising technique to develop improved IVIVCs of a complete dosage form, and the FaSSIFmod is suitable to predict the possible absorption rate-limiting steps of poorly soluble drugs in DDASS.

To develop a new bionic system from an existing drug dissolution/absorption simulating system (DDASS) to simultaneously predict the release and absorption of enteric-coated formulations. In accordance with the pH-dependent characteristics of enteric-coated formulations, the modified DDASS was designed to effectively imitate the pH change process of the formulations' transfer from stomach to intestine in vivo. Omeprazole enteric-coated tablets were chosen as the model drug to verify the rationality and feasibility of the modified DDASS. The correlations between USP I system release and beagle dog absorption, as well as between modified DDASS elution/permeation and beagle dog absorption, were investigated by linear and nonlinear regression analyses, respectively. In vitro-in vivo correlation between the modified DDASS elution/permeation method and beagle dog absorption was higher than between the USP I system release and beagle dog absorption in both analytical methods. The ratio of first-order permeation rate constant to first-order release rate constant was consistent with that from modified DDASS. The modified DDASS provided more information than the USP I system did in the evaluation of enteric-coated formulations. The proposed bionic system model could serve as a new method for improving drug effectiveness.

The objective of this study was to develop and validate the in vitro-in vivo correlations (IVIVCs) of three commercially available immediate-release solid dosage forms of indapamide using drug dissolution/absorption simulating system (DDASS). The in vitro dissolution profiles of three brands of immediate-release tablets were obtained using the USP I basket method and DDASS. A single-dose, three-way, crossover pharmacokinetic study for the tablets was carried out in six beagle dogs. Correlation models were developed for each immediate release formulation using cumulative percentage dissolved/eluted (Fd) versus cumulative percentage absorbed (Fa) and cumulative percentage permeated (Fp) versus cumulative percentage absorbed (Fa). Prediction errors were estimated for the Cmax and AUC to determine the validity of the correlation. Level A IVIVCs were established for the three brands between in vitro (dissolution and permeation) data from DDASS and in vivo data from dogs. Predicted plasma concentrations of each commercial brand were obtained from the dissolution and permeation profile data using the correlation models. A percent prediction error of