Effect of Swelling and Drug Release Relationship of Sustained Release Matrices Containing Different Grades of Hydroxypropyl Methylcellulose

Sustained release diclofenac sodium matrices are used to achieve a prolonged therapeutic effect by continuously releasing medication over an extended period of time after administration of a single dose for analgesic, antipyretic and anti- inflammatory activities. The current study examines the relationship between swelling and drug release from the hydrophilic matrices of diclofenac sodium matrices prepared using combination of different grades of hydroxypropyl methylcellulose (HPMC), viz, HPMCK4M, HPMCK15M and HPMCK100M. The Degree of Swelling and Percent water uptake were determined for the matrices containing different concentrations and combinations. The results indicate that swelling and release profiles were affected by concentration and viscosity grade of the polymer. When the amount of HPMC in the matrix is high, wetting improves and water uptake into matrices is enhanced. The higher amount of HPMC causes a greater degree of swelling this in turn reduces the drug release, as the diffusional path length of drug is now longer. Conversely, reduction in the amount of HPMC reduces the degree of swelling and the thickness of gel layer, this enables faster drug release. Higher viscosity grades swells to greater extent and has greater intrinsic water uptake property than that of the lower viscosity grades. Swelling studies reveals an inverse relationship between swelling and drug release in the sustained release diclofenac sodium matrices.