In situ Gel of Metoprolol Tartrate: Physicochemical Characterization, In vitro Diffusion and Histological Studies

The purpose of the present investigation was to prepare an intranasal in situ gel with increased nasal residence time in order to improve bioavailability of metoprolol tartrate. The in situ gel systems containing carbopol, hydroxypropyl methylcellulose K4M and K15M in different concentrations were prepared. The samples were characterized for viscosity, rheological behavior, gelation behavior, gel strength, and mucoadhesion. The formulations F10 (0.4% w/v carbopol, 1% w/v hydroxylpropyl methylcellulose K15M) and F13 (0.3% w/v carbopol, 1% w/v hydroxypropyl methylcellulose K15M) showed gel strength of 40.33±0.47 and 43.00±1.41, respectively, and mucoadhesion strength 31.48±0.14×10(3) and 32.12±0.05×10(3) dyne/cm(2), respectively. In vitro release profiles showed initial burst followed by slow release. F10 and F13 released 88.08±0.98 and 91.18±1.09% drug in 8 h. R(2) value for F10 (0.9953) and F13 (0.9942) was maximum for Higuchi, showing mixed order kinetics while n value obtained on treatment with Korsemayer Pappas equation were near to 0.5, suggesting release by fickian diffusion mechanism. The nasal permeability of formulations F10 and F13 were found to be 0.057 and 0.063 cm/s, respectively. Histopathological examination revealed slight degeneration of nasal epithelium with increased vascularity by F10 but no inflammation by formulation F13. Thus, a pH triggered in situ gel system containing low concentration (0.3% w/v) of carbopol demonstrated sustained release of metoprolol tartrate without any destructive effect on the mucosa.