Poly(lactide-co-glycolide) microspheres containing bupivacaine: comparison between gamma and beta irradiation effects.

The beta- and gamma-irradiation effects on stability of microspheres made of poly(lactide-co-glycolide) 50:50 copolymer (PLGA) containing bupivacaine (BU) were studied. Microspheres containing 10, 25, and 40% w/w, respectively, of BU were prepared by spray drying and irradiated in air with beta- and gamma-irradiation at a dose of 25 kGy. Morphology (atomic force microscopy, particle-size analysis), physico-chemical characteristics (DSC and FT-IR spectroscopy), drug content and in vitro dissolution profile of microspheres were all determined; the stability of irradiated microspheres was evaluated over a 9-month period. The decrease of BU content in gamma-irradiated microspheres was almost always constant independent of the amount of BU per sample, therefore it was in inverse proportion to drug loading (range between 5 and 15%). BU release rate increased immediately after irradiation and increased slightly until 90 days of storage. As far as beta-irradiated microspheres are concerned, BU content decreased in a significant way (approximately 3%) only in microspheres containing 10% w/w of BU. Immediately after irradiation, drug release rate in beta-irradiated microspheres increased less than in the corresponding gamma-irradiated microspheres, and it did not change further over the following storage period. BU-loaded microspheres have been shown to be more stable against beta- than gamma-irradiation. AFM revealed that the surface roughness of the irradiated microspheres increases depending on irradiation. As such, if a parameter is quantifiable, it is proposed as a marker of degradation due to ionizing radiation.

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 T(g) 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