Formulation development and in vitro evaluation of gastroretentive hollow microspheres of famotidine

BACKGROUND

The main aim of this study was to develop a gastroretentive, multiple-unit floating drug delivery system for a drug which is poorly absorbed from the lower gastrointestinal tract. Such a dosage form may provide an extended retention of drug in the upper gastrointestinal tract resulting in enhanced absorption and improved bioavailability.

MATERIALS AND METHODS

Microspheres were prepared by the emulsion solvent diffusion method. Four different ratios (1:1, 1:2, 1:3, and 1:4) from each polymer, i.e., Eudragit RL 100 (E1-E4) and cellulose acetate (C1-C4) were prepared.

RESULTS

Hollow microspheres were characterized by particle size using optical microscopy. The in vitro release data obtained for the formulations E1-E4 and C1-C4 showed good entrapment efficiency, good percentage buoyancy, and prolonged drug release. The in vitro drug release showed the highest regression coefficient values for Higuchi's model, indicating diffusion to be the predominant mechanism of drug release. The surface and cross-sectional morphology of the formulations E1-A and C1-A were determined using scanning electron microscopy.

CONCLUSIONS

Thus, prepared floating hollow microspheres of famotidine may prove to be potential candidates for the multiple-unit drug delivery device adaptable for any intragastric condition.

Development of hollow microspheres as floating controlled-release systems for cardiovascular drugs: preparation and release characteristics

Hollow microspheres of cellulose acetate loaded with four cardiovascular drugs (nifedipine [NFD], nicardapine hydrochloride [NCD], verapamil hydrochloride [VRP], and dipyridamole [DIP]) were prepared by a novel solvent diffusion-evaporation method. The oil-in-water emulsion prepared in an aqueous solution of 0.05% poly(vinyl alcohol) medium with ethyl acetate, a water-soluble and less toxic solvent, was used as the dispersing solvent. The yield of the microspheres was up to 80%. The microspheres had smooth surfaces, with free-flowing and good-packing properties. Scanning electron microscopy (SEM) confirmed their hollow structures, with sizes in the range 489-350 microm. The microspheres tended to float over the gastric media for more than 12 h. The drug loaded in hollow microspheres was in an amorphous state, as confirmed by differential scanning microscopy (DSC). The release of the drugs was controlled for more than 8 h. The release kinetics followed different transport mechanisms depending on the nature of the drug molecules.

Microspheres as floating drug-delivery systems to increase gastric retention of drugs

Gastric emptying is a complex process, which is highly variable and makes in vivo performance of the drug-delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug-delivery systems for more than 12 h. The floating or hydrodynamically controlled drug-delivery systems are useful in such applications. The present review addresses briefly the physiology of the gastric emptying process with respect to floating drug-delivery systems. In recent years, the multiparticulate drug-delivery systems are used in the oral delivery of drugs. One of the approaches toward this goal is to develop the floating microspheres so as to increase the gastric retention time. Such systems have more advantages over the single-unit dosage forms. The development of floating microspheres involves different solvent evaporation techniques to create the hollow inner core. The present review addresses the preparation and characterization of the floating microspheres for the peroral route of administration of the drug.