pH sensitive

Nasal mucosa has been considered as a potential administration route to achieve faster and higher levels of drug absorption because it is permeable to more compounds than the gastrointestinal tract. It is an attractive route of administration due to lack of pancreatic and gastric enzymatic activity, neutral pH of the nasal mucus and less dilution by gastrointestinal contents. In-situ gel forming systems have been developed to prolong the nasal residence time of a drug and improve nasal bioavailability. Fexofenadine hydrochloride is one of the most widely used drugs for allergic rhinitis. It is an anti-histaminic and is available in oral dosage forms. The present work is aimed at designing a gel formula for nasal administration. To enhance therapeutic effect of the nasal formulation of fexofenadine hydrochloride pH sensitive polymers were used. Xanthan gum and Carbopol 934 were selected as independent variables in the factorial design. Solubility of the drug in the formulation was enhanced by using Tween 80. Evaluation parameters of the formulation like pH, clarity; rheological study both formulation i.e. solution and performed gel, gelling time, drug content, in-vitro drug diffusion study, stability studies were performed. The formulations so designed shall enhance bioavailability of drug and offer better therapeutic outcomes, offer aesthetically appealing dosage form to increase patient compliance and shall overcome side effects and limitations of other dosage forms of marketed preparations.

The major goal of any drug delivery system is to supply a therapeutic amount of drug to the target site in the body, in order to achieve desired drug concentration. Colon targeted drug delivery system involves the targeting of drug to colon and is used for the treatment of various diseases related to colon like inflammatory bowel disease, colon cancer, crohn’s diseases etc. Targeting to colon directly reduces the need of higher dose, dosing frequency, incidence of side effects and cost effective treatment can also be achieved. Colon was considered as “BLACK BOX” and generally absorption of most drugs occur in upper G.I region. Lack of digestive enzymes and delayed gastric emptying, has given the idea to design colon specific drug delivery system. This review article compares the different approaches to colon targeted drug delivery like pH and time dependent, prodrug, microbial triggered and pulsatile drug delivery system etc. Beside these different new approaches were also used for colon targeting like pressure controlled, osmotic controlled drug delivery systems are highly effective.