title: Rapid elevation of gentamicin levels in the human labyrinth following intravenous administration.
abstract: OBJECTIVE
  Adequate quantities of labyrinthine fluid can be sampled from the human labyrinth to perform quantitative analysis of medications. A rapid elevation of intralabyrinthine gentamicin levels after intravenous administration can be measured. A model for the sampling of human inner ear fluid in this manner is described.
  
  
  BACKGROUND
  The risk of aminoglycoside ototoxicity has been a long-standing concern. The kinetics of gentamicin diffusion into the inner ear have been extrapolated to humans from various animal models. The validity of extrapolation to humans is unknown. We have developed a new model to measure the uptake of gentamicin in vivo.
  
  
  METHODS
  A single intravenous dose of gentamicin (80 mg) was given perioperatively to 13 patients undergoing translabyrinthine acoustic neuroma surgery. The lateral semicircular canal and vestibule were opened and a microsyringe was used to obtain a sample of labyrinthine fluid concomitant with a serum sample. The gentamicin concentration of the labyrinthine fluid and serum was analyzed using a standard chemistry analyzer.
  
  
  RESULTS
  After parenteral administration of gentamicin, fluid was obtained from the inner ear of 13 acoustic neuroma patients. Inner ear concentrations were between 1.0 and 3.8 mg/L. Serum gentamicin levels ranged from 1.2 to 10.5 mg/L.
  
  
  CONCLUSIONS
  This method allows the sampling of intralabyrinthine fluid in humans. Gentamicin was noted immediately in the labyrinth after intravenous administration. This model may be expanded to measure other compounds given either by intravenous or transtympanic routes.
authors.affiliation: Michigan Ear Institute, Farmington Hills, Michigan 48334, U.S.A.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Becvarovski
authors.forename: Elias M
authors.initials: EM
authors.lastname: Michaelides
authors.forename: Jack M
authors.initials: JM
authors.lastname: Kartush
authors.forename: Dennis I
authors.initials: DI
authors.lastname: Bojrab
authors.forename: Michael J
authors.initials: MJ
authors.lastname: LaRouere
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000032:analysis*; D007758:Ear, Inner; D005260:Female; D005839:Gentamicins / Q000008:administration & dosage / Q000032:analysis*; D006801:Humans; D007275:Injections, Intravenous; D007761:Labyrinthine Fluids / Q000737:chemistry*; D008297:Male; D008875:Middle Aged
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins