Abstract
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.
Highlights
The use of biodegradable polysaccharides has gained wide acceptance in the development of controlled drug delivery systems
In erosion tests run in phosphate buffer, both types of beads exhibited an initial increase in volume
This feature was observed throughout the drug release tests and is probably the main cause underlying the prolonged release of the drug from the beads
Summary
The use of biodegradable polysaccharides has gained wide acceptance in the development of controlled drug delivery systems. Over the past few decades, natural biodegradable polysaccharides such as pectin, guar gum, chitosan, carrageenans, sodium alginate (Na-alginate), hydroxypropyl methylcellulose (HPMC), agar and gellan gum have been widely used (Kulkarni et al 2001; Sriamornsak, et al 2004) These polymers can be exploited in various ways in the formulation of targeted and controlled drug delivery as they have different derivatizable groups, a wide range of molecular weight, and varying chemical composition. Bead formation is obtained by incorporation of the drug into a gel dispersion system, and the hydrophilic colloids (Gonzalez-Rodrıguez et al 2002) interact with polyvalent metal ions to form insoluble colloidal complexes (calcium alginate), droplets that will precipitate in bead form This system is generally formed by ionotropic cross-linking of natural biodegradable polysaccharides, but the resulting calcium alginate bead is usually very permeable, making it very difficult to control drug release for a prolonged period of time (Lin, Ayres 1992; Østberg et al 1994; Ferreira, Almeida 2004). Release characteristics in different pH ranges, entrapment efficiency, polymer morphology, swelling capacity and erosion were investigated
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