New insights on poly(vinyl acetate)-based coated floating tablets:: Characterisation of hydration and CO2 generation by benchtop MRI and its relation to drug release and floating strength

The purpose of this study was to investigate the mechanism of floating and drug release behaviour of poly(vinyl acetate)-based floating tablets with membrane controlled drug delivery. Propranolol HCl containing tablets with Kollidon (R) SR as an excipient for direct compression and different Kollicoat (R) SR 30 D/Kollicoat (R) IR coats varying from 10 to 20 mg polymer/cm(2) were investigated regarding drug release in 0.1 N HCl. Furthermore, the onset of floating, the floating duration and the floating strength of the device were determined. In addition, benchtop MRI studies of selected samples were performed. Coated tablets with 10 mg polymer/cm(2) SR/IR, 8.5:1.5 coat exhibited the shortest lag times prior to drug release and floating onset, the fastest increase in and highest maximum values of floating strength. The drug release was delayed efficiently within a time interval of 24 h by showing linear drug release characteristics. Poly(vinyl acetate) proved to be an appropriate excipient to ensure safe and reliable drug release. Floating strength measurements offered the possibility to quantify the floating ability of the developed systems and thus to compare different formulations more efficiently. Benchtop MRI studies allowed a deeper insight into drug release and floating mechanisms noninvasively and continuously. (C) 2007 Elsevier B.V. All rights reserved.