Colon targeting

The aim of the study was to develop colon targeted tablets of Sulfasalazine (SSZ) by wet granulation method using 33 Response surface method with design of experiment software and Eudragit RS 100, Eudragit RL 100-55, Ethyl cellulose and PVP K-30 as pH dependent polymers. All the formulations (F1 to F27) were evaluated for the physicochemical parameters and were subjected to in vitro drug release studies. The amount of Sulfasalazine released from tablets at different time intervals was estimated by UV spectrophotometer. The formulation F17 shown 98.21±1.15 of Sulfasalazine after 24 h, whereas marketed product drug release was 96.21±1.87 after 1 h. The results of the study showed that formulation F17 is the best formulation on the basis of drug release and other evaluation parameters. From in vivo bioavailability studies, after oral administration of colon targeted tablet containing 500 mg Sulfasalazine, the Cmax, Tmax, and AUC0–∞ of optimized formulation and marketed product was found to be 684.31±4.03 ng/mL, 6.01±0.04 h, 4525.12±2.02 ng*h/ mL and 702.26±3.23 ng/mL, 1.50±0.01h, 3335.18±2.02 ng*h/mL respectively. Cmax, Tmax and AUC values of optimized formulation were found to be significantly higher than of marketed product. The pH dependent system is a promising vehicle for preventing rapid hydrolysis in gastric environment and improving oral bioavailability of Sulfasalazine in the effective management of colon related diseases.

Lornoxicam is a non steroidal anti-inflammatory drug of oxicam class and it has the same side effects of this group when taken orally and has a relatively short plasma half-life (3 to 4 h) which makes it a good candidate for colon targeting. It could avoid the systemic side effects, enhance its low oral bioavailability due to hepatic first pass metabolism and delay drug release to target the colon. Eighteen tablet formulations of lornoxicam were prepared by wet granulation and coated with different polymers (pectin, chitosan, ethyl cellulose, cellulose acetate phthalate, eudragit L-100 and eudragit L-100-55), each at three concentration. The tablets were evaluated for their physical characters, in–vitro dissolution in gradient pH, as well as, mathematical modeling using DDSolver software package. The dissolution data best fitted to first order with Tlag model with Krosmyer Pepas (n) values around unity suggesting erosion mechanism for all tablets except pectin coated ones which showed Fickian diffusion mechanism. Fitting the release data to the different erosion models suggested heterogeneous erosion mechanism. Lornoxicam tablets coated with 6% Eudragit L-100 were successfully delivered to the colon with a relative bioavailability of 531.96% compared to the conventional commercial tablets in rabbits.

The potential of guar gum as a film coating material for colon targeted delivery of raupyabhasma is assessed in this study. The granules was prepared by mixing raupyabhasma, guar gum and xanthan gum which was coated by guar gum and pH-sensitive polymer eudragit FS30D sequentially around drug-loaded granules. The outer eudragit FS30D coating defends the system against gastrointestinal environment and dissolves rapidly in distal small intestine, where a lumen pH of over 7 triggers the dissolution of the enteric polymer. The inner guar gum coating works as a time-controlled retardant and offers additional protection of the granules until it is degraded by microbes at the proximal colon. In vitro results indicate that guar gum followed by eudragit FS30D coating is a feasible coating material to achieve colon specific drug delivery.

The aim of the study was to formulate colon targeted diclofenac sodium alginate beads. The beads were formulated by ionotropic gelation using sodium alginate as polymer, calcium carbonate as an internal cross linking agent and calcium chloride as an external cross linking agent. The optimized beads contained Neusilin and coated with Eudragit L100. The beads were analyzed in terms of, encapsulation efficiency (EE%), particle size and morphology. Swelling properties were studied in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.4). In vitro drug release was studied in SGF, pH 1.2, SIF, pH 6.8 and SIF, pH 7.4. The results show that the particle size of the beads ranged from 1.98 ± 0.40 to 2.80 ± 0.30 mm. The optimized batch containing Neusilin® had the highest EE% of 72 % significantly higher than other batches (p < 0.05). The degree of swelling of the beads was zero in SGF and about 90 % in SIF at 100 min. The results of the in vitro release showed that the beads had 0 % release in SGF, pH, 1.2 at 2 h, about 3 % in SIF, pH 6.8 at 4 h and 9 % drug release in SIF, pH 7.4 at 9 h. Therefore, sodium alginate beads could be used for colon delivery of diclofenac sodium. 

  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.