Ekarat Jantratid. Feasibility studies on biowaiver extension of In Vivo bioequivalence of class III drugs based on the biopharmaceutics classification system . Doctoral Degree(Pharmaceutics). Mahidol University. : Mahidol University, 2005.
Feasibility studies on biowaiver extension of In Vivo bioequivalence of class III drugs based on the biopharmaceutics classification system
Abstract:
The general concept of biowaiver is to use in vitro dissolution testing as a surrogate for in vivo bioequivalence assessment. The feasibility of extending this concept to drugs belonging to Class III of the Biopharmaceutics Classification System (BCS) using cimetidine as a model drug was evaluated in this study. The BCS-conform dissolution tests were carried out on ten marketed cimetidine products as well as on three cimetidine tablet formulations manufactured by direct compression using methacrylate copolymer (Eudragit® RS PO) as a release-modifier. Twelve Thai healthy male subjects were enrolled in a treatment schedule based on a five-way Williams design. Subjects received treatments including Tagamet® tablet, 7.5%, 15% and 26% Eudragit® RS PO cimetidine tablets and Tagamet® intravenous injections, with a one-week washout period between treatments. The pharmacokinetic parameters were evaluated and statistically compared among formulations. In silico simulations using the computer programs PK-Sim® and STELLA® were also conducted to predict drug absorption in vivo. The marketed cimetidine products dissolved rapidly, in compliance with the BCS criteria, while the release of the cimetidine tablet formulations differed considerably from one another. However, in vivo results showed no significant difference in the pharmacokinetic parameters with the exception of the mean residence time values obtained from 26% Eudragit® RS PO tablets, which were significantly longer than those from the other tablet formulations. The in vitro-in vivo correlation (IVIVC) analysis demonstrated that the 26% Eudragit® RS PO tablets exhibited dissolution rate limited absorption, whereas the other formulations were permeability rate-limited. Computational simulations showed fair correlation compared with in vivo results. On the in vitro side, it seems that the Food and Drug Administration indicated dissolution criteria are more than sufficient to guarantee bioequivalence of immediate-release cimetidine products. In conclusion, extension of the biowaiver concept to BCS Class III drugs seem to be feasible and appropriate