02013nas a2200241   4500008004100000022001400041245008600055210006900141260009000210300001000300490000700310520116100317653001401478653001201492653002001504653001901524653001901543653001701562653002201579100002201601700003201623856011601655       2012                        eng d  a0363-904500apH Sensitive graft copolymers for zero order drug release: a mechanistic analysis0 apH Sensitive graft copolymers for zero order drug release a mech  aTELEPHONE HOUSE, 69-77 PAUL STREET, LONDON EC2A 4LQ, ENGLANDbINFORMA HEALTHCAREcJAN  a73-830 v383 a<p>Aliphatic polyesters containing pendent unsaturation were synthesized by the polycondensation of a diol, dicarboxylic acid and glycidyl methacrylate. Grafting methacrylic acid (MAA) resulted in graft copolymers containing polyester backbone and MAA grafts. Depending on composition, the polymers swelled extensively and eroded or dissolved at near neutral pH but remained in collapsed state at acidic pH. Three representative drugs differing in solubility, viz., Diltiazem hydrochloride (DH), Indomethacin (IM) and Verapamil hydrochloride (VH) were released at constant rate from tablets made by compressing spray-dried microparticles. The release of DH at constant rate has been attributed to increase in diffusion coefficient of the drug from the swollen layer of matrix. The release of IM and VH at constant rate was governed by erosion and was enhanced in matrices which undergo dissolution. The release rate was enhanced with increasing MAA content and the frequency of grafts along the polyester backbone. Once a day dosage forms for drugs differing in solubility have been developed using a single polymer matrix which is easy to manufacture.</p>10aDiffusion10aerosion10aGraft copolymer10amatrix tablets10amicroparticles10aspray drying10asustained release1 aMuthusamy, Ramesh1 aKulkarni, Mohan, Gopalkrish  uhttps://library.ncl.res.in/content/ph-sensitive-graft-copolymers-zero-order-drug-release-mechanistic-analysis-0