title: Analysis of the initial burst of drug release coupled with polymer surface degradation.
abstract: OBJECTIVE
  Local pH effect on the release of a model pH-inert hydrophobic drug coupled with polymer degradation is described at the induction phase of biodegradable polymer erosion for better understanding the nature of initial burst of a drug.
  
  
  METHODS
  Using a novel approach with time-of-flight secondary ion mass spectrometry. both surface concentration of Ph3N and degradation kinetics of PLLA are simultaneously and independently determined from a model Ph3N/PLLA (20:80 wt%) blend matrix (t approximately 0.4 microm on 1.0 cm2). In vitro hydrolysis of the model blend matrix is investigated for short-term periods (<24 h) at physiologic pH and temperature and compared to basic pH.
  
  
  RESULTS
  The rate of PLLA degradation is accelerated by a factor of approximately 3 when using basic pH in vitro, but the rate of Ph3N accumulation at the surface is accelerated by a factor of approximately 6.
  
  
  CONCLUSIONS
  A new quantitative method has been developed to examine the earliest stages of polymer degradation and drug release. It was applied to a model system that could not be examined by traditional in vitro methods. For the model system studied the release of a low molecular weight hydrophobic drug at the induction phase of polymer erosion is related to but not singularly dependent on degradation kinetics.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA.
authors.forename: Joo-Woon
authors.initials: JW
authors.lastname: Lee
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Gardella
authors.forename: Wesley
authors.initials: W
authors.lastname: Hicks
authors.forename: Robert
authors.initials: R
authors.lastname: Hard
authors.forename: Frank V
authors.initials: FV
authors.lastname: Bright
mesh_terms: D004364:Pharmaceutical Preparations / Q000032:analysis* / Q000378:metabolism*; D011108:Polymers / Q000032:analysis* / Q000493:pharmacokinetics*; D013499:Surface Properties
chemical_list: D004364:Pharmaceutical Preparations; D011108:Polymers