THE INFLUENCE OF DRUGS ON THE PROPERTIES OF GELS AND SWELLING CHARACTERISTICS OF MATRICES CONTAINING METHYLCELLULOSE OR HYDROXYPROPYLMETHYLCELLULOSE

The cloud points, matrix swelling and gel layer formation in matrices containing cellulose ethers and indomethacin, propranolol hydrochloride or tetracycline hydrochloride have been investigated. The two hydrochloride salts contributed to the matrix swelling and gel layer formation, maintaining the integrity of matrices containing methylcellulose. Gel layer formation, measured by thermomechanical analysis was most rapid, and the layer thickest, in matrices containing propranolol hydrochloride. This mimicked cloud point determination where propranolol salted the cellulose ethers into solution to a greater extent than tetracycline. The poorly soluble indomethacin failed to contribute to swelling and gel layer formation. Studies, using U-tube viscometry, indicated that the viscosity of gels containing HPMC E4M, HPMC F4M, HPMC K4M and methylcellulose reduced on storage. This appeared to be further catalysed by the inclusion of drugs, and especially of tetracycline hydrochloride in the gels.