title: In vitro elution of gentamicin from Plaster of Paris beads.
abstract: OBJECTIVE
  To determine the in vitro elution characteristics of gentamicin from Plaster of Paris-gentamicin (POP-gent) beads.
  
  
  METHODS
  In vitro, controlled, experimental study.
  
  
  METHODS
  The POP-gent beads were made using a bead mold from 20 g calcium sulfate hemihydrate, 5 mL (500 mg) gentamicin solution, and 3 mL of phosphate buffered saline (PBS). Control beads were made similarly, using 30 g of dried powder and 8 mL of PBS. Beads were left in the mold overnight, gas-sterilized with ethylene oxide, and stored at room temperature for 5 months before testing. Bead chains were placed in sterile tubes containing porcine serum, and tubes were placed in a 37 degrees C incubator on a rocker. Serum was removed at intervals over 14 days and the concentration of gentamicin determined by fluorescent polarization immunoassay. Serum antibacterial activity was determined against an equine origin Escherichia coli.
  
  
  RESULTS
  POP-gent beads released gentamicin for the 14-day sampling period. Eighty percent of the gentamicin incorporated in the beads was released over the first 48 hours. Eluent from POP-gent beads inhibited the growth of E coli at all time periods. No gentamicin was eluted from control beads and control eluent did not inhibit growth of E coli.
  
  
  CONCLUSIONS
  In this experimental model, POP-gent beads released bactericidal drug for 14 days. Eighty percent of the gentamicin incorporated into the beads was released during the first 48 hours. The drug retains its bactericidal activity after ethylene oxide sterilization and storage at room temperature for up to 5 months.
  
  
  CONCLUSIONS
  Pop-gent beads may be a useful repository device to deliver gentamicin locally in tissues.
authors.affiliation: College of Veterinary Medicine, University of Minnesota, St. Paul, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Santschi
authors.forename: Lisa
authors.initials: L
authors.lastname: McGarvey
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D002133:Calcium Sulfate; D003692:Delayed-Action Preparations; D004356:Drug Storage; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary*; D005839:Gentamicins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D008826:Microbial Sensitivity Tests; D010019:Osteomyelitis / Q000188:drug therapy / Q000662:veterinary*; D013552:Swine
chemical_list: D000900:Anti-Bacterial Agents; D003692:Delayed-Action Preparations; D005839:Gentamicins; D002133:Calcium Sulfate