The influence of substitution type on the performance of methylcellulose and hydroxypropylmethycellulose in gels and matrices

Abstract

The characteristics of matrices containing hydroxypropylmethylcellulose (HPMC) grades E4M, F4M or K4M, or methylcellulose A4M have been compared using thermomechanical analysis, differential scanning calorimetry (DSC), laser analysis, cloud points and via the dissolution of a model drug, propranolol hydrochloride, from matrices containing the cellulose ethers and prepared by direct compression. Dissolution rates of propranolol varied according to the drug/cellulose ether ratio within the matrix. Propranolol release from methylcellulose matrices was least affected by this ratio but the performance differences of the three grades of HPMC could not be distinguished. In the absence of drug, matrices containing methylcellulose disintegrated at 37 and 44°C. Water uptakes, as measured by DSC and gel layer thicknesses, were similar for each grade of cellulose ether. Matrices containing HPMC K4M tended to swell to the greatest extent. For all grades, swelling was greater in the axial rather than radial direction. Cloud points provided the best prediction of matrix performance.