Local delivery of Antiparasitic drugs to the colon as a treatment for Colonic Diseases

  Amoebiasis is an infection of the large intestine caused by Entamoeba histolytica, and it is mainly present in the intra-intestinal lumen. The efficient treatment of amoebiasis and other colonic infections could be achieved by targeting the drug to the colon. Tinidazole is the drug of choice for intestinal amoebiasis and other colon infections and the best approach for this drug is to target the drug delivery to colon which would make the drug effective with low dose and prevent the potential hazards observed in conventional dose. The objective of the present investigation was to design a multiparticulate delivery system for site-specific delivery of Tinidazole using natural polysaccharides (pectin) and pH-sensitive polymer (Shellac) for the treatment of colonic diseases. An attempt was made to prepare and characterize Tinidazole microspheres for colon specific drug delivery in order to target the drug to the colon. Pectin microspheres were prepared using emulsion cross- linking technique. These microspheres were coated with Shellac using oil-in-oil solvent evaporation method. The method was optimized using different drug: polymer ratio (1:2, 1:3, 1:4 and 1:5) stirring rate (500, 1000, 1500, and 2000) and emulsifier concentration (1%, 1.25%, 1.5% and 2%) to produce microspheres of small size and narrow size distribution, high drug loading efficiency, and controlled drug release at the colonic pH. Microspheres prepared by using drug: polymer ratio 1:3, stirring speed 1000 rpm, and 1.25% w/v concentration of emulsifying agent were selected as an optimized formulation. Microspheres were evaluated for surface morphology, particle size and size distribution, swellability, percentage drug entrapment, in- vitro drug release in simulated gastrointestinal fluids (SGF) and stability study. The experimental results demonstrated that the prepared microspheres of Tinidazole for colon targeting may reduce the side effects of the drug caused by its absorption from the upper part of GIT when given in conventional dosage forms. Key words: Tinidazole; Amoebiasis; Colon targeting; Shellac; Pectin microspheres.