Estimation of the percolation thresholds in lobenzarit disodium native dextran matrix tablets

Abstract

The objective of the present work is to estimate for the first time the percolation threshold of a new series of dextran (native dextran of high molecular weight [B110-1-2, Mw = 2 x 10(6)]), in matrices of lobenzarit disodium (LBD) and to apply the obtained result to the design of hydrophilic matrices for the controlled delivery of this drug. The formulations studied were prepared with different amounts of excipient in the range of 20% to 70% wt/wt. Dissolution studies were performed using the paddle method (100 rpm) and one face water uptake measurements were performed using a modified Enslin apparatus. The Higuchi, zero-order, and Hixson-Crowell models as well as the nonlinear regression model were employed as empiric methods to study the release data. Values of diffusion exponent 0.563 < n < 0.786 (Korsmeyer equation) for dissolution profile and water uptake mechanism 0.715 < n < 1 (Davidson and Peppas equation) suggested anomalous or complex mechanisms. On the other hand, the contribution of the relaxation or erosion and of the diffusive mechanism in Peppas-Sahlin equation indicated that the main mechanism for drug delivery from tablets is swelling controlled delivery (K(r)/K(d) < 1). The critical points observed in kinetic parameters above 58.63% vol/vol of native dextran B110-1-2 plus initial porosity in the LBD-dextran matrices with a relative polymer/drug particle size of 4.17 were attributed to the existence of an excipient percolation threshold.

Superabsorbent hydrogels based on polysaccharides for application in agriculture as soil conditioner and nutrient carrier: A review

“…The water within the hydrogel dissolves the nutrient, which can diffuse through polymer network. The movement of solutes toward the outside of the hydrogel can be related with swelling rate [179,180]. Not all load of the substance in the hydrogel is released.…”

Determining the Polymer Threshold Amount for Achieving Robust Drug Release from HPMC and HPC Matrix Tablets Containing a High-Dose BCS Class I Model Drug: In Vitro and In Vivo Studies

“…Dissolution profiles for formulation A5 containing HPC (0) and for formulation B5 containing HPMC (right) obtained from various dissolution testing methods DT1-DT4 (Table II) To evaluate the release mechanism, the diffusion coefficient n was calculated using the Korsemeyer-Peppas approach (Table VI). In addition, we also calculated the ratio of K r /K d after fitting the dissolution data using the Peppas-Sahlin equation (27,28). For all of the calculations, we used dissolution data for which approximately 60% of the drug was dissolved.…”

“…In addition, the dissolution profiles were fitted using the Peppas-Sahlin equation (Eq. 2) (27,28). Origin software from OriginPro labs was used.…”

Dextran and its potential use as tablet excipient

“…Moreover, dextrans have been extensively utilized as controlled release polymer excipients in the preparation of oral hydrophilic matrix tablets [19][20][21][22][23].…”