The Preparation and Evaluation of Albendazole Microspheres for Colonic Delivery

rug delivery to the colon is beneficial not only for the oral delivery of proteins and peptide drugs (degraded by digestive enzymes of stomach and small intestine) but also for the delivery of low molecular weight compounds used to treat diseases associated with the colon or large intestine such as ulcerative colitis, diarrhea, and colon cancer. In addition, the colon has a long retention time and appears highly responsive to agents that enhance the absorption of poorly absorbed drugs. The approaches used in the colonic delivery of drugs include the use of prodrugs (1), pH-sensitive polymer coatings (2, 3), time-dependent formulations (4), bacterialdegradable coatings (5), time pH-controlled deliveries (6), and intestinal luminal pressure-controlled colon delivery capsules (7). In addition, the use of biodegradable polymers such as azopolymers and polysaccharides (e.g., pectins and dextrans) for colon targeting has also been described in the literature (8, 9). Several publications have described drug-containing microspheres using the Eudragit (Rohm Pharma) series of polymers as the encapsulating materials (10, 11). The Eudragits are a family of polymers based on acrylic and methacrylic acids suitable for use in orally administered drug delivery systems. These polymers are available in various grades possessing a range of physicochemical properties. Some dissolve rapidly at clearly defined pH values, whereas two grades, Eudragit RL and RS, are insoluble in aqueous media but permeable, and as such have been shown to be suitable for sustained-release microencapsulated dosage forms. The permeability of Eudragit RL and RS to aqueous solutions results from the presence of quaternary ammonium groups in their structure; RL has a higher proportion of these groups and as such is more permeable than RS. In recent years, microsphere dosage forms have gained increasing importance as oral controlled drug delivery systems. These systems present several advantages in comparison to unit dosage forms such as more predictable gastric emptying and less local irritation (12). Microsphere systems also minimize the possible intestinal retention of undigested polymer materials in chronic dosing (13). As part of a research program to investigate the controlled and targeted delivery of drugs to the colon, Eudragit RL polymer (ERLP) microspheres containing albendazole were prepared. Albendazole, used to treat parasites, was selected for colon delivery D