163 Research Papers JPP 2005, 57: 163–168 ß 2005 The Authors Received August 24, 2004 Accepted October 26, 2004 DOI 10.1211/0022357055362 ISSN 0022-3573 Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria Oluwatoyin A. Odeku School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Manchester M13 9PL, UK John T. Fell Correspondence: Oluwatoyin A. Odeku, Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria. E-mail: pejuodeku@yahoo.com Funding: We wish to acknowledge the MacArthur Foundation and the University of Ibadan for a MacArthur Foundation Staff Development Grant awarded to O. A. Odeku. In-vitro evaluation of khaya and albizia gums as compression coatings for drug targeting to the colon Oluwatoyin A. Odeku and John T. Fell Abstract Khaya and albizia gums were evaluated as compression coatings for target drug delivery to the colon using indometacin (a water insoluble drug) and paracetamol (a water soluble drug) as model drugs. The core tablets were compression-coated with 300 and 400 mg of 100% khaya gum, 100% albizia gum and a mixture of khaya and albizia gum (1:1). Drug release studies were carried out in 0.1 M HCl (pH 1.2) for 2 h, Sorensen’s buffer (pH 7.4) for 3 h and then in phosphate-buffered saline (pH 6.8) or in simulated colonic fluid for the rest of the experiment to mimic the physiological conditions from the mouth to colon. The results indicated that khaya and albizia gums were capable of protecting the core tablet in the physiological environment of the stomach and small intestine, with albizia gum showing greater ability than khaya gum. The release from tablets coated with the mixture of khaya and albizia gums was midway between the two individual gums, indicating that there was no interaction between the gums. Studies carried out using rat caecal matter in phosphate-buffered saline at pH 6.8 (simulated colonic fluid) showed that the gums were susceptible to degradation by the colonic bacterial enzymes, leading to release of the drug. The results demonstrate that khaya gum and albizia gum have potential for drug targeting to the colon. Introduction Target drug delivery to the colon is highly desirable for local treatment of diseases such as colon cancer and inflammatory bowel disease, and the systemic delivery of protein and peptide drugs. A colonic drug delivery system is expected to protect the drug during the transit time in the gastrointestine and to allow its release only in the colon. This delivery system has the advantages of more effective therapy, a reduced dose and reduced undesirable side-effects often associated with high doses (Ashford et al 1993a, b). The various approaches that have been studied for targeting orally administered drugs to the colon include the use of pH-sensitive polymers (Ashford et al 1993a, b; Khan et al 1999), time-dependent dosage forms (Davis et al 1986; MacNeil & Stevens 1990; Van den Mooter & Kinget 1995), and the use of carriers degraded by enzymes produced by colonic bacteria (Rama Prasad et al 1998; Sinha & Kumria 2002). Of these approaches, the use of materials that are degraded by the colonic microflora has been found to be the most promising because of their site specificity (Rama Prasad et al 1998). A number of plant polysaccharides have been investigated as carriers for colon- specific drug delivery based on the activity of colonic bacteria on the carrier systems. The polysaccharides that have been investigated include pectin and its salts (Rubinstein et al 1993; Ashford & Fell 1994; Wakerly et al 1996a, b; Munjeri et al 1997), amylose (Milojevic et al 1996), chitosan (Tozaki et al 1997), and guar gum (Rama Prasad et al 1998; Krishnaiah et al 1998a, b). These polysaccharides are capable of protecting the drug from being released in the acidic environment prevailing in the stomach and small intestine: they are degraded by the colonic bacterial enzymes, thereby releasing the drug in the colon where there is local action and improved absorption. The fact that these polysaccharides are naturally available, inexpensive, non-toxic and biodegradable has also increased interest in developing them for phar- maceutical use. Downloaded from https://academic.oup.com/jpp/article/57/2/163/6147382 by guest on 16 February 2022