Alginate/hydrophobic HPMC (60M) particulate systems: new matrix for site-specific and controlled drug delivery

this study aimed to obtain site-specific and controlled drug release particulate systems. some particulates were prepared using different concentrations of sodium alginate (na-alg) alone and others were formulated using different proportions of na-alg with hydroxypropyl methylcellulose (hpmc) stearoxy ether (60m viscosity grade), a hydrophobic form of conventional hpmc, using diclofenac potassium (dp) by ion-exchange methods. beads were characterized by encapsulation efficiency, release profile, swelling, and erosion rate. the suitability of common empirical (zero-order, first-order and higuchi) and semi-empirical (ritger-peppas and peppas-sahlin) models was studied to describe the drug release profile. the weibull model was also studied. models were tested by non-linear least-square curve fitting. a general purpose mathematical software (matlab) was used as an analysis tool. in addition, instead of the widely used linear fitting of log-transformed data, direct fitting was used to avoid any sort of truncation or transformation errors. the release kinetics of the beads indicated a purely relaxation-controlled delivery, referred to as case ii transport. weibull distribution showed a close fit. the release of dp from na-alg particulates was complete in 5-6 hours, whereas from na-alg hydrophobic hpmc particulate systems, release was sustained up to 10 hours. hydrophobic hpmc with na-alg is an excellent matrix to formulate site-specific and controlled drug release particulate systems.