Development Of IN Pellets For Microbially Triggered Colon Drug Delivery

Objectives: In the recent years, oral colon-specific drug delivery system (OCDDS) has been broadly used, because it can be used to the treatment of pathological changes of site in colon. Natural polysaccharide polymer is widely used as excipient, which is to become new carrier excipient of colon-specific drug delivery system, because it can be specifically degradated by enzyme released from colon flora. Alginate is water-soluble, nontoxicity and biocompatible. Alginate is a natural polysaccharide polymer isolated from seaweeds oralgae, which is widely used as a sustained- release and controlled-release excipient of tablets, pellets, microspheres, liposome and nanoparti-cle.ALG/CaCl₂ microbially triggered colon drug delivery system could release the drug in the colon, which use alginate as excipient and IN as drug. The drug delivery system could increase the drug concentration of the colon and reduce the side effect.Methods: Pellet containing alginate were prepared by the process of gelatinating reaction of alginate and CaCl2, which form the hydrophobicity backbone frame. The drug fit-into the backbone fram. The special enzyme in colon could degradate the backbone frame and release the drug, that achieved colon-specific delivery of drug after oral.Pectin aqueous solution including IN at a concentration was prepared. This dispersion was added drop-wise, using a nozzle, into CaCl2 solution of the cross-linking agent, forming the IN ALG/CaCl2 pellets. The single factor experiment was designed to screen technique in the dropper diameter, speed of dropping, temperature of drying and time of drying. The orthogonal experiment was designed to screen prescription in which CaCl2 solution concentration, alginate solution concentration and CaCl2 solution pH were taken as three influential factors and two different levels were selected to part, each conformation of prescription was selected according to the L4(23)orthogonal design table. By analysis of range, the optimization of technique was definite with the colligation evaluation of formation and percent of release.The UV and HPLC analytical method was found upon reference and preliminary experiment. Drug release studies in the presence of caecal content were carried out according to USP 23 and reference.The chemical and physical stability of optimal formula was investigated under following circumstances: high humidity, high temperature and strong light. In the fifth day and the tenth day of the study period, the formulation was observed for change in physical appearance, color and drug release characteristics.The animals were divide into two groups. Each group administered orally IN pellets or IN suspension via a polyethylene cannula (diameter: 3 mm) with 1ml water under light ether anesthesia. The IN concentrations in plasma, stomach, small intestine, cecum and colon were determined by high performance liquid chromatography after administered.Results: The pellet were prepared with optimization artwork: dropper diameter 0.9 mm; speed of dropping 2 ml/min, temperature of drying 45℃, time of drying 24 h. The results of the study show that CaCl2 solution concentration, alginate solution concentration and CaCl2 solution pH is the major effect of the release of pellets in vitro. The decibel analysis of orthogonal experiment show the optimization prescription: CaCl2 solution concentration 1%, alginate solution concentration 2%, CaCl2 solution pH 4.The results of the system serve experiment of the HPLC method to determine the content of IN: the reserve time of IN were about 9.995 min, the recoveries were between 93.80%～101.8%, the precision was below 3%. The method could determine the content of IN accurately and precisely.There was no change in the physical appearance and percent of release of the IN pellets at the end of the high temperature study. The pellets get heavy moisture absorption at the end of the high moisture study. That means the pellets should be reserved aridity. There was no change in the physical appearance of the IN pellets at the end of the strong light study, while there is a light of decrease in the percent of release. That means the pellets should be reserved away from light.The mean peak IN concentrations in cecum and colon, respectively, were 1.24±0.15μg/g and 1.97±0.26μg/g for IN released from the pellets, and 0.22±0.05μg/g and 0.58±0.09μg/g for the administration of the suspension. In plasma, the high and sharp drug concentration profile from suspension was in contrast to the relatively low and flat pharmacokinetic profile obtained from drug released from the pellets. In contrast, the observed mean CBmax B from the pellets group (6.26±1.08μg/mL) was lower than that of the uncoated pellets group (10.14±1.89μg/mL). There was a statistically significant difference (p<0.05) in the AUC values between the suspension (88.67±8.34μg·h/mL) and pellets (71.35±2.56μg·h/mL). The relative bioavailability of the pellets is 80.47% by comparing the AUC under the assumption that the BA of IN released from the suspension is 100%.Conclusions: Combination of alginate and CaCl2 as adjuvant may provide the necessary protection to a drug in the upper GI tract while allowing enzymatic breakdown and drug release in the colon. The distribution of IN pellets was markedly different from that of IN suspension after oral administration. In contrast to suspension dispersal along the whole upper GI tract, IN was predominantly released from the pellets in cecum and colon. The absorption of drug from different regions of the GI tract was found to influence the pharmacokinetic profile and parameters.In conclusion, colon-specific delivery of IN was achieved after oral administration of the ALG/CaCl2 pellets to the rats. The relatively high local drug concentration with prolonged exposure time provides a potential to enhance colon disease efficacy with low side effect for the treatment.