In vitro study of some factors affecting the adhesive strength of mucoadhesive polymers

Mucoadhesive drug delivery systems are among novel drug delivery systems that due to their ability to adhere and remain on the mucosal surfaces and a slow and sustained release of their drug content have attracted special attention in recent years. The aim of this study was to evaluate the effect of four different important factors on the mucoadhesive strength of a few mucoadhesive polymers. Among the polymers investigated, apart from the known polymers such as Carbopol 934P (C934) and sodium carboxymethyl cellulose (CMC) which have high mucoadhesive strengths, the effectiveness of a few other polymers were also studied. These were polyethylene oxide (PEO), Karaya (Kar), Carrageenan (Carr) and sodium alginate (Na alg). For this purpose polymer containing discs were prepared and their mucoadhesive strength in rat intestine (As a mucosa model) was assessed by using a home made apparatus. The mucoadhesive strength of prepared polymeric discs in the presence and absence of phosphate buffer pH=6.0 at 37°C and at various pH values from 2.2-8.0, and under the condition of hydrating the polymeric discs for 2 and 5 minutes in phosphate buffer pH=6.0 before placing them in contact with mucosa, was evaluated. Also, the effect of urea (As the hydrogen bond breaker) on the mucoadhesive strength of discs containing C934 and PEO was evaluated. The results showed that among the polymers studied, PEO and Carr like C934 and CMC have desirable mucoadhesive strengths, and could be used for the preparation of mucoadhesive drug delivery systems. It was also found that the extent of hydration of polymer containing discs has an important effect on their mucoadhesive strength. In case of insufficient polymer hydration or its overhydration, the mucoadhesive strength will be greatly reduced. Also, the environmental pH has an important effect on their mucoadhesive strength of discs and therefore in the design of a mucoadhesive system, a polymer with a high mucoadhesive strength in the specific area of the body should be used. Furthermore it was found that the formation of hydrogen bonds between the mucoadhesive polymer and mucosa, plays a very important role in the formation of a strong mucoadhesive bond.