The influence of concentration on the release of drugs from gels and matrices containing Methocel®

Formulation and evaluation of glipizide floating-bioadhesive tablets

“…The thermodynamic state of the polymer and the penetrant concentration are responsible for the different types of the diffusion. A third class of diffusion is case II diffusion, which is a special case of non-Fickian diffusion (Peppas 1985;Mitchell et al 1993). The results of the calculated n (Table 3) revealed a non-Fickian type of drug diffusion, which meant that the process of diffusion and relaxation ran at comparable rates.…”

“…The tablets composed of a polymeric matrix build a gel layer around the tablet core on contact with gastric fluid, which controlled the drug release. Drug release from HPMC matrices is controlled by diffusion through the gel layer for water-soluble drugs or by erosion of the outer polymer chains for poorly soluble drugs (Mitchell et al 1993). The drug characteristics are as important as those of the gel.…”

Simultaneous quantification of drug release and erosion from hypromellose hydrophilic matrices

“…Rapid gel layer formation around the matrix tablet is an essential feature that can dictate drug release regardless of solubility of drug. Higher amounts of HPMC form a quicker but stronger gel layer which is more resistant to diffusion 275 and/or erosion (Mitchell et al, 1993) .…”

“…At higher levels of HPMC the increased concentration leads to chain entanglement which increases the tortuosity of matrix tablets (Chaibva et al, 2010;Mitchell et al, 1993) 265 and can be considered a decisive feature impeding the diffusion of drug from the matrix gel layer during dissolution. An additional factor can be a lower porosity, as higher amount of HPMC corresponds to low matrix tablet porosity which exhibits low liquid movement across the surface of matrix tablet and leads to slower drug release rates (Reza et al, 2003).…”

Evaluation of Physical Properties as Magnesium Stearate Blendedin Hydrophilic Matrix Tablets

“…41, No. 2 (2011) factors, including the physicochemical properties of the components, their compositions and ratios in the formulations, and manufacturing process parameters can influence the drug release behavior from the final drug products (Mitchell et al, 1993;Gao et al, 1996;Campos-Aldrete and Villafuerte-Robles, 1997).…”