title: Release Pattern of Liposomal Bupivacaine in Artificial Cerebrospinal Fluid.
abstract: OBJECTIVE
  We aimed to compare the possible controlled release profile of multilamellar liposomal bupivacaine formulations with non-liposomal forms in artificial cerebrospinal fluid (CSF) under in vitro conditions.
  
  
  METHODS
  Liposome formulations were prepared using a dry-film hydration method. Then, an artificial CSF-buffered solution was prepared. Bupivacaine base with liposomal bupivacaine base, bupivacaine HCl with liposomal bupivacaine HCl and bupivacaine HCl were added in a Franz diffusion cell. These solutions were kept in a hot water bath for 24 h. The samples were taken at 0.5, 1, 3, 6, 12 and 24 h (1st series of experiment). Solutions of bupivacaine base with liposomal bupivacaine base and bupivacaine HCl with liposomal bupivacaine HCl were centrifuged to obtain liposomal bupivacaine base and liposomal bupivacaine HCl. Afterwards, liposomal bupivacaine base and liposomal bupivacaine HCl were added in a Franz diffusion cell. After keeping these solutions in a hot water bath for 24 h as well, the samples were taken at the same time intervals (2(nd) series of experiment). All samples (54 from the 1st experiment and 36 from the 2(nd) experiment) were analysed with high-performance liquid chromatography and ultra-performance liquid chromatography and their chromatograms were obtained.
  
  
  RESULTS
  After obtaining calibration curves for bupivacaine base and HCl, release patterns of these formulations were plotted. A markedly controlled slow-release pattern was observed for multilamellar liposomal bupivacaine than for non-liposomal bupivacaine in artificial CSF.
  
  
  CONCLUSIONS
  Demonstration of controlled slow-release profile for mutilamellar liposomal bupivacaine in artificial CSF in vitro might support intrathecal use of liposomal bupivacaine in vivo in animal studies.
authors.affiliation: Department of Anesthesiology and Reanimation, Gazi University School of Medicine, Ankara, Turkey.
authors.forename: Ayşe Ünal
authors.initials: AÜ
authors.lastname: Düzlü
authors.affiliation: Department of Anesthesiology and Reanimation, Gazi University School of Medicine, Ankara, Turkey.
authors.forename: Berrin
authors.initials: B
authors.lastname: Günaydın
authors.affiliation: Department of Pharmaceutical Chemistry, Gazi University School of Pharmacy, Ankara, Turkey.
authors.forename: Murat Kadir
authors.initials: MK
authors.lastname: Şüküroğlu
authors.affiliation: Department of Pharmaceutical Technology, Gazi University School of Pharmacy, Ankara, Turkey.
authors.forename: İsmail Tuncer
authors.initials: İT
authors.lastname: Değim
keywords: Liposome; bupivacaine; cerebrospinal fluid; controlled slow release