Pharmaceutical and pharmacokinetic evaluation of novel rectal mucoadhesive hydrogels containing tolmetin sodium

The objective of the present study was to develop rectal mucoadhesive hydrogels loaded with Tolmetin Sodium, a non-steroidal anti-inflammatory drug, for prolonged duration of action and increased bioavailability. Fourteen formulae were prepared with different types and concentrations of polymers as hydroxypropylmethyl cellulose, hydroxylethyl cellulose, carboxymethyl cellulose and sodium alginate. Each formulation contain Tolmetin Sodium equivalent to 5% w/w active drug. The effect of the employed gel bases on pH, gel strength, mucoadhesion, viscosity and the in vitro release profile of drug was examined. In addition, hydrogel formulations were subjected to rheological and stability studies. The physicochemical characterization revealed that all hydrogels had a suitable pH (6.64–7.75) and gel strength (15.5–65.29 s) for rectal application. The in-vitro drug release from the formulations showed a controlled drug release pattern, reaching 72–92.6% after 8 h. The kinetic analysis of the release data revealed that the drug release from all tested hydrogel bases obeyed the diffusion mechanism. The degradation of Tolmetin Sodium from its rectal hydrogel formulations was found to be a zero-order reaction. All formulations except sodium alginate hydrogel were quite stable. Considering the in-vitro release, rheological properties and shelf life, (CMC; 2%w/w) hydrogel formula was the best among the studied formulations. Therefore, further histopathological and bioavailability studies were carried out to detect different pharmacokinetic parameters of the established formulations compared with commercially available capsules. Formula containing 2% CMC showed relative bioavailability 357.93%. Finally, good correlation was observed between in-vitro and in-vivo profile.