methylcellulose and lobenzarit

The aim of this work is to estimate the excipient percolation threshold for a new combined matrix native dextran (DT), series B110-1-2 (Mw 2 x 10(6)): HPMC K4M CR: lobenzarit disodium (LBD) system and demonstrate the advantages of this ternary system with respect to previously reported binary dextran:LBD and HPMC:LBD tablets. The formulations studied were prepared with different amounts of excipient (DT:HPMC, 4:1 (wt/wt) for all tablets and relative polymer/drug particle size of 4.17) in the range of 10-70% (wt/wt). Dissolution studies were carried out using the paddle method (100 rpm) and one face water uptake measurements were performed using a modified Enslin apparatus. The Higuchi's models as well as the non-linear regression were employed as empiric methods to study the released data. Values of diffusion exponent 0.588

Topics: Dextrans; Lactose; Methylcellulose; ortho-Aminobenzoates; Porosity; Tablets; Technology, Pharmaceutical

In previous papers of our research group, a linear relationship between the drug percolation threshold and the relative drug particle size (drug/excipient) has been found, in the case of the inert matrices. The objective of the present paper is to investigate the influence of the particle size on the excipient percolation threshold in the case of hydrophilic matrices. This influence can have important consequences on the release behaviour of these controlled release devices. Matrix tablets have been prepared using KCl/Lobenzarit Disodium as drugs and HPMC K4M as matrix forming material, employing six different excipient/drug particle size ratios (ranging from 0.42 to 4.16). The formulations studied contain a drug loading in the range of 20-90% (w/w). In order to estimate the percolation threshold, the behaviour of the kinetic parameters with respect to the volumetric fraction of each component at time zero, was studied. The obtained results support the existence of a linear relationship between a component percolation threshold (drug or excipient) and its relative particle size (drug/excipient in the case of the drug percolation threshold or excipient/drug in the case of the excipient percolation threshold). This relationship is valid for different drugs, excipients and systems (inert or hydrophilic matrix tablets).

Topics: Chemistry, Pharmaceutical; Delayed-Action Preparations; Drug Compounding; Excipients; Hypromellose Derivatives; Kinetics; Linear Models; Methylcellulose; Models, Chemical; ortho-Aminobenzoates; Particle Size; Porosity; Potassium Chloride; Reproducibility of Results; Solubility; Tablets; Technology, Pharmaceutical