Influence of neutron irradiation on Eudragit (R) coated tablets: validation of neutron activation II

The in vitro characteristics of enteric coated acetylsalicylic acid tablets and cores were compared before and after irradiation with thermal neutrons , 2, 4, 7 or 15 min at 1.1 . 10(13) neutrons cm(-2) s(-1). The irradiation procedure affected the coated formulation to a greater extent than the core s. Drug release from tablets was already affected after 2 min of exposure, whereas the cores showed no significant inhibition of release until after 1 5 min of irradiation, leading to the conclusion that the effects of irradia tion were caused by a combination of changes both in the core and the coati ng. Both tablets and cores showed an increase in the disintegration time fo llowing irradiation. Scanning electron micrographs (SEM) of non-irradiated cores/tablets and cores/tablets irradiated for 15 min, showed clear differe nces in the structure of the surface. SEM of the tablets irradiated for 15 min, showed that the irradiation had caused the him to loosen from the core in several places. SEM of the cross-sections of both irradiated tablets an d cores showed a partially melted surface above stacked layers with reduced porosity. (C) 1999 Elsevier Science B.V. All rights reserved.