In vitro of some bfactors affecthng the adhesive strength of mucoadhesive polymers

Mucoadhesive durg delivery systems are among novel drug delivery systems that due to their ability to adhere and remain on the mucosal surfaces and a show and sustained release of their drug contect 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 nof 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 mucose model) was assessed by using a home made apparatus.the mucoadhesive  strength  of prepared polymeric discs in the presence and obsence of phosphate buffer PH=6.0  at 37C 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 uera (as the hydrogen bond breaker) on the mucoadhesive strength of discs contatining 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 od hydration of polymer containing discs has an important effect on their mucoadhesive strength.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 the mucoadhesive strength of discs and therefore in the desing of a mucoadhesive system,a polymer whit a high mucoadhesive strength in the specific area of the boys should be used.Furthermore it was found that the formation of hydrogen bonds between the mucoadhesive polymer and mucose,plays a very important role min the fprmation of a strong mucoadhesive bond.