Matrix or monolithic devices consist of drug dispersed homogenously throughout a continuous phase of polymer or lipid. The devices can be prepared either by the compression of a polymer/drug mixture or by the dissolution or melting, resulted in the molecularly dispersed drug. The drug transport often results from a combination of several mechanisms included dissolution, diffusion, swelling and erosion.
Figure 4: Matrix system for single unit dosage form
Water-soluble matrix formers
Water-soluble or hydrophilic matrices are a well-known type of ER oral dosage forms. While hydroxyl propyl methylcellulose (HPMC) is the most important hydrophilic carrier material, several others are also availableincluding:
(i) Cellulose derivatives: hydroxyl propyl cellulose (HPC), carboxy methylcellulose sodium (NaCMC).…show more content… Following a proper preparation method, the ER pellets are either filled into a capsule or are compressed into a tablet.
The matrix type of multiparticulate systems can be prepared by several techniques such as extrusion/spheronisation, spherical crystal agglomeration and melt-solidification. Although, the production of multiparticulate matrix systems is considered to be easier than that of the reservoir systems, their extent of retardation is limited because of pellet geometry.
Coated pellets as a mean to control drug delivery are widely used in the pharmaceutical industry, although the development and optimization of the systems are rather complex. Numerous aspects of the system performance have been investigated, for instance, the influence of formulation and coating technique, the effect of drug solubility and core material, the use of polymer blends, in vitro/in vivo evaluation and the influence of release