Influence of pH on the Release of Propranolol Hydrochloride from Matrices Containing Hydroxypropylmethylcellulose K4M and Carbopol 974

Abstract

The dissolution of propranolol hydrochloride from matrices containing hydroxypropylmethylcellulose K4M (HPMC K4M) and carbopol 974 has been investigated using 0.1 M hydrochloric acid or phosphate buffer at pH 4.5 or pH 7.5. In 0.1 M hydrochloric acid, HPMC K4M predominantly controlled release since carbopol has a low solubility at this pH. As the pH increased, the carbopol became increasingly ionized and interacted with propranolol hydrochloride to form an insoluble complex which retarded the release of the drug. In addition, the nature of the interaction between carbopol 974 and HPMC K4M altered. DSC and viscometric studies indicated that the two polymers contributed synergistically to the gel network at pH 7.5. Thus at pH 7.5 polymers contributed to matrix integrity and to the control of drug release.

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

“…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.…”

Development of Polymeric Blend Microspheres from Chitosan-Hydroxypropylmethyl Cellulose for Controlled Release of an Anti-Cancer Drug

“…11 The drug release from HPMC-tablets can be modified by changing variables such as the viscosity grade or the particle size of HPMC, 12,13 or the HPMC: filler ratio or HPMC: drug ratio, 14−16 or the solubility of the filler 17 or by the addition of other hydrophilic polymers. 18 Depending on the solubility of the drug, the drug is primarily released either by diffusion through a gelled layer or erosion of this layer.…”

Use of .BETA.-Cyclodextrins to Prevent Modifications of the Properties of Carbopol Hydrogels Due to Carbopol-Drug Interactions.

“…[8][9][10] The nature of such interactions varies (ionic interaction, hydrogen bonds, etc. ), depending on the characteristics of the polymer and the drug.…”

“…The Carbopols are high-molecular-weight carboxyvinylic derivatives comprising polyacrylic acid subunits crosslinked with allyl saccharose or pentaerithritol allyl ethers. PRP is known to interact with polyacrylic acid, 10) and to form stable inclusion compounds with CDs (binding constant of 220Ϯ20 M Ϫ1 at pH 7 calculated using liquid chromatography method). 12) We investigated the effects of carbomer/drug interactions on the principal characteristics of the system, namely drug solubility, swelling, drug release and bioadhesiveness.…”