Release of bupivacaine from artificial ligament implants modified with the silica coating

Abstract

Post-operative pain is an important health problem that may delay patients' rehabilitation. In surgery, to treat pain, local anesthetics such as bupivacaine are used to effectively reduce post-operative discomfort. The aim of this study was to investigate the release of the bupivacaine from proposed implants and to test the storage stability of implants. The implants were obtained using sol-gel method and the release of the bupivacaine was carried out employing apparatus flow through cell connected to the UV–Vis spectrophotometer. The absorbance of the acceptor fluid was obtained at selected time intervals and the amount of the drug released was calculated. The obtained release profiles were analyzed employing the zero-, first-, second-order kinetics and Higuchi, Korsmeyer-Peppas and Hixon-Crowell models. Based on these equations the release rate constants and the half release time as well as the coefficient of determination were calculated. It was found that the model that the best described the release profile of bupivacaine was zero-order or Higuchi equation. All release profiles were also characterized well by Hixon-Crowell model. The dissolution profiles of the drug were compared deriving the difference factor f1 and the similarity factor f2. The comparison was also carried out employing the statistical methods such as ANOVA with Tukey's HSD test and Student's t-test. It was revealed that all compared release profiles were different. The observed discrepancies between bupivacaine dissolution profiles were connected with the coating preparation. The storage study of I5 implants showed that the amount of bupivacaine released after 6 months of storage was lower indicating the possibility of its decomposition.