PREPARATION OF THEOPHYLLINE-LOADED CALCIUM ALGINATE GEL CAPSULES AND EVALUATION OF THEIR DRUG-RELEASE CHARACTERISTICS

A method for the preparation of theophylline-loaded alginate gel capsu les was developed, and their drug release characteristics were investi gated. A dispersion containing theophylline and wheat starch suspended in a calcium chloride solution was dropped into a sodium alginate sol ution. The calcium ions then diffused out of the droplets and reacted with the alginate, resulting in the formation of a water-insoluble cal cium alginate gel membrane around each droplet. In subsequent drying, spherical, glossy capsules with a smooth surface were obtained (an ave rage diameter of 3.1 mm). The coat thickness increased with coating ti me, and the CaCl2, concentration in the core dispersion increased. The efficiency of drug encapsulation (EE) decreased with an increase of t he coating time, and increased with an increase of the CaCl2, concentr ation and the theophylline loading dose in the core dispersion. The co at thickness and EE were almost independent of the sodium alginate con centration in coating fluids (1% and 2%). The theophylline release fro m the gel capsules followed zero-order kinetics, and the release rates were significantly reduced as the coat thickness increased. Furthermo re, the release rates were greatly reduced compared with those of the matrix-type alginate gel beads.