Polymethacrylate salts as new low-swellable mucoadhesive materials

The sodium and potassium salts of the methacrylic copolymers Eudragit® L100 and Eudragit® S100 were prepared with the aim to develop new low-swellable mucoadhesive materials intended for the preparation of buccal dosage forms. The physico-chemical characterization of the copolymers and the corresponding sodium and potassium salts was performed by using Fourier-transform infrared (FT-IR) spectroscopy and thermal analysis. When ionization occurred, the carboxylic acid group absorption band (1730 cm-1) was replaced by another characteristic band at 1560 cm-1. After salification the Tg of the two polymers shifted towards higher values and it was not significantly influenced by the contraion nature. The intrinsic dissolution rate at infinite rotation speed (7.354<G∞<9.196) was about 6- to 7-fold higher than that of a low nominal viscosity hydroxypropylmethylcelluloses (HPMC). Moreover, the Eudragit® salts did not show an evident swelling layer and their dissolution is governed by erosion. The adhesion properties of these materials, evaluated by texture analysis, overlapped with those of Carbopol® 934P. On the basis of the in vivo bioadhesion test, the prepared methacrylic salts can be considered interesting for the preparation of both buccal tablets and patches with good patient compliance due to their low swelling properties.