title: Confocal Raman-spectroscopy: analytical approach to solid dispersions and mapping of drugs.
abstract: OBJECTIVE
  To compare the physical state of a drug in a liquid with a polymeric matrix.
  
  
  METHODS
  Solid solutions of ibuprofen in polyvinylpyrrolidone were obtained from the hot melt extrusion technique. In order to investigate the physicochemical stability, content, and homogeneity of the formulation, the tablets produced by a subsequent calendering step were examined using confocal Raman spectroscopy. In addition, a dimeric vinylpyrrolidone was synthesized and used to compare the physical state of embedding in a polymeric matrix with a physical solution of the active in a solvent, i.e. the dimeric vinylpyrrolidone. The spatial resolution of confocal Raman spectroscopy was used to image the drug distribution in the final form.
  
  
  RESULTS
  Confocal Raman spectroscopy has been successfully used to determine the state of ibuprofen in a solid matrix showing equivalence to a physical solution. Moreover, the physicochemical stability of the formulation under stress conditions and content, as well as homogeneity of drug distribution in the formulation matrix, has been examined with the same method, proving the efficiency of the approach.
  
  
  CONCLUSIONS
  Confocal Raman spectroscopy offers a new approach for the analytical assessment of solid dispersions both covering the physical state as well as the distribution of the drug via its spatial resolution. Moreover, it is a promising tool for observing changes in a formulation due to physicochemical processes, e.g. recrystallisation and at the same time for locating the area where changes occur. Therefore, it may contribute to standard analytical methods to evaluate content and homogeneity.
authors.affiliation: Knoll AG, New Business/Extrusion, Ludwigshafen, Germany. joerg.breitenbach@knoll-ag.de
authors.forename: J
authors.initials: J
authors.lastname: Breitenbach
authors.forename: W
authors.initials: W
authors.lastname: Schrof
authors.forename: J
authors.initials: J
authors.lastname: Neumann
mesh_terms: D000284:Administration, Oral; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D055598:Chemical Phenomena; D002626:Chemistry, Pharmaceutical / Q000379:methods; D002627:Chemistry, Physical; D004355:Drug Stability; D007052:Ibuprofen / Q000737:chemistry*; D018613:Microscopy, Confocal / Q000379:methods*; D011205:Povidone / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D011205:Povidone; D007052:Ibuprofen