title: In vitro and in vivo drug release from a novel in situ forming drug delivery system.
abstract: OBJECTIVE
  The objective of this work was to investigate the influence of various preparation and formulation parameters on the in vitro and in vivo release of bupivacaine hydrochloride from an injectable in situ forming microparticle system (ISM).
  
  
  METHODS
  The in vitro drug release of ISM was investigated as a function of various formulation and process parameters and was compared to the drug release from in situ forming implants and conventional microparticles. In vivo studies were carried out in male Sprague-Dawley rats.
  
  
  RESULTS
  Upon contact with an aqueous medium, the internal polymer phase of the ISM system solidified and formed microparticles. The initial drug release from ISM systems was reduced with decreasing polymer phase/external oil phase ratio. An advantage of the ISM system compared to in situ implant systems was the significantly reduced burst effect, resulting in drug release profiles comparable to microparticles prepared by conventional methods. The in vivo drug release studies were in good agreement with the in vitro drug release. With the ISM system, the analgesic effect of the bupivacaine hydrochloride was prolonged when compared to the injection of a drug solution or drug-polymer solution.
  
  
  CONCLUSIONS
  ISM are an attractive alternative for parenteral drug delivery systems.
authors.affiliation: College of Pharmacy, Freie Universität Berlin, Berlin, Germany. Heiko.Kranz@bayerhealthcare.com
authors.forename: Heiko
authors.initials: H
authors.lastname: Kranz
authors.forename: Erol
authors.initials: E
authors.lastname: Yilmaz
authors.forename: Gayle A
authors.initials: GA
authors.lastname: Brazeau
authors.forename: Roland
authors.initials: R
authors.lastname: Bodmeier
mesh_terms: D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems; D019344:Lactic Acid / Q000737:chemistry; D008297:Male; D011100:Polyglycolic Acid / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
chemical_list: D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D002045:Bupivacaine