Studies on the Interaction Between Water and (Hydroxypropyl)Methylcellulose

Abstract

The moisture sorption and desorption profiles of four different viscosity grades of (hydroxypropyl)methylcellulose (HPMC) 2208 (HPMC K100, HPMC K4M, HPMC K15M, and HPMC K100M) of different particle size fractions were analyzed according to the Young and Nelson equations. These equations describe three locations of the sorbed moisture: monolayer adsorption, externally adsorbed moisture, and internally absorbed moisture. The effects of particle size and viscosity grade of HPMC on the three locations of moisture showed that an increase in particle size generally resulted in a reduction in the amount of internal absorption and an increase in the amount of external adsorption. These changes were more apparent for HPMC K100 and HPMC K4M than for the higher viscosity grades. The lowest values of internally absorbed moisture were obtained for HPMC K100M. Changes in tensile strengths, mean yield pressures, and elastic recoveries of HPMC K4M tablets were explained in terms of the changes produced in the internally absorbed moisture and the externally adsorbed moisture. The amounts of nonfreezing and freezing water in samples exposed to moisture were determined from melting endotherms obtained by differential scanning calorimetry. Increases in the water:HPMC ratio resulted in increases in the enthalpies of water melting for the four viscosity grades of HPMC for the < 45 and 250-350 microns particle size fractions. The amount of nonfreezable water was unaffected by change in viscosity grade or particle size.

Formulation development of oral controlled release tablets of hydralazine: Optimization of drug release and bioadhesive characteristics

“…On the other hand, the value of n at low levels of CP increases to an asymptote with an increasing amount of HPMC. Thus, the current results seem to be in agreement with the findings of Nokhodchi et al (24), indicating an ambiguous relationship of n with the change in polymer composition. The corresponding contour plot (Fig.…”

“…Relatively high magnitudes of the Fickian diffusion constant, k 1 , vis-à-vis the polymer relaxation constant, k 2 , clearly show that the drug release was predominantly determined by Fickian diffusion, with negligible contribution of polymer relaxation. This is in consonance with several research findings that a mixture of HPMC with CP results in the reduction of polymer viscosity owing to reduced hydration of the matrix and facilitating drug diffusion through the polymer hydrogel (14,16,23,24). Table III reveals that the overall rate of drug release tended to decrease with an increase in concentration of HPMC or CP.…”

The Effect of Moisture on the Flowability of Pharmaceutical Excipients

“…With the exception of PVP, all of the powders showed s-shaped adsorption isotherms indicating type II isotherms. This type of isotherm has also been reported in the literature for these powders (8,9,14,(25)(26)(27). PVP showed a type III isotherm with the moisture content increasing very rapidly at high air humidities; Oksanen and Zografi (6) also reported a type III isotherm for PVP.…”

Effect of Polymorphism on the Particle and Compaction Properties of Microcrystalline Cellulose

“…The product A is related to the amount of water in the monolayer and A(+B) is the externally adsorbed moisture during the sorption phase. B is the amount of moisture absorbed during the sorption phase [21].…”