title: Influence of the inlet air temperature in a fluid bed coating process on drug release from shellac-coated pellets.
abstract: BACKGROUND
  Since the introduction of aqueous ammoniacal solutions, shellac regained importance for pharmaceutical applications. However, as shellac is a material obtained from natural resources, its quality and thus its physicochemical properties may vary depending on its origin and the type of refining.
  
  
  OBJECTIVE
  In this study theophylline pellets were coated with aqueous solutions of three different commercially available shellac types. The inlet air temperature of the coating process was varied, and its influence on drug release from the coated pellet formulations was investigated. Film formation was correlated to the physicochemical and mechanical properties of the investigated shellac types.
  
  
  RESULTS
  Pellets coated at lower temperatures showed distinct cracks in the coating film resulting in a loss of the barrier function during dissolution testing. These cracks were nonreversible by additional curing. The physicochemical and mechanical properties of the investigated shellac types varied significantly and could hardly be related to the drug release performance of the investigated formulations.
  
  
  CONCLUSIONS
  Obviously, with shellac a minimum inlet air temperature must be exceeded to achieve a coherent coating film. This temperature was dependent on the investigated shellac type.
authors.affiliation: Department of Pharmaceutical Technology, Institute of Pharmacy, University of Hamburg, Germany.
authors.forename: Yassin
authors.initials: Y
authors.lastname: Farag
authors.forename: Claudia Sabine
authors.initials: CS
authors.lastname: Leopold
mesh_terms: D000388:Air; D001993:Bronchodilator Agents / Q000737:chemistry*; D055598:Chemical Phenomena; D004304:Dosage Forms; D016503:Drug Delivery Systems; D004343:Drug Implants; D005079:Excipients / Q000737:chemistry*; D012116:Resins, Plant / Q000737:chemistry*; D012995:Solubility; D012996:Solutions; D013696:Temperature; D013718:Tensile Strength; D013806:Theophylline / Q000737:chemistry*; D044366:Transition Temperature; D014867:Water / Q000737:chemistry
chemical_list: D001993:Bronchodilator Agents; D004304:Dosage Forms; D004343:Drug Implants; D005079:Excipients; D012116:Resins, Plant; D012996:Solutions; D014867:Water; C003934:shellac; D013806:Theophylline