A STUDY OF THE HYDROPHILIC CELLULOSE MATRIX - EFFECT OF INDOMETHACIN AND A WATER-SOLUBLE ADDITIVE ON RELEASE MECHANISMS

The release profile of indomethacin (IM) from a direct compressible ma trix containing three hydrophilic cellulose derivatives, methylcellulo se (MC25 and MC50), hydroxypropylcellulose (HPC140), and hydroxypropyl methylcellulose (HPMC50) was studied. The drug release profile was aff ected by matrix size, polymer type, drug:polymer ratio and water solub le additive (lactose). An IM zero-order release matrix: can be obtaine d by mixture and direct compression with MC50, HPMC50 and HPC140. The release rate from the MC50 and HPC140 matrix can be modified by replac ing MC50 or HPC140 with MC25, and a zero-order release could be obtain ed even when the amount of replacement with MC25 is up to 35 and 45%, respectively, Lactose up to 10% slightly affected the release profile. IM released from this kind of matrix by a zero-order rate seems to be controlled by the swelling and relaxation of the polymer.