Mucoadhesive dosage form of lidocaine hydrochloride: I. Mucoadhesive and physicochemical characterization.

The aim of this study was to characterize a buccal mucoadhesive film using lidocaine and its hydrochloride salt (LDHCL) as a model drug. Buccal films were developed using carbopol 971P as a mucoadhesive polymer, and glycerol as a plasticizer. Scanning Electron Microscope, Differential Scanning Calorimetry, X-ray powder diffraction, and Fourier Transform Infra Red techniques were used to characterize the mucoadhesive films. Bioadhesive properties were evaluated using the Universal Instron Instrument with chicken pouch as a model tissue. LDHCL and its base were present in carbopol 971P films in a molecular dispersion state without exerting any effect on the glass transition of these films. The mucoadhesive force between the chicken pouches and the film containing glycerol did not change by time during the tested period (1-20 min), while increased with increasing the amount of glycerol (10-40% w/w of polymer content). Furthermore, a linear increase in the mucoadhesive force was accompanied by the increase in the film thickness, while a linear decrease followed by plateau was obtained when loading the patch with LDHCL at concentration above 1 mg/cm(2). Loading carbopol film with lidocaine base, in a concentration up to 6 mg/cm(2) decreased linearly the mucoadhesive properties, which could be attributed to salt formation between the acidic carboxylic moiety of carbopol and basic lidocaine.