title: Analysis of gentamicin kinetics in fluids of the inner ear with round window administration.
abstract: OBJECTIVE
  That a theoretical basis for quantifying drug distribution in the inner ear with local applications can be established.
  
  
  BACKGROUND
  As methods of local drug delivery to the inner ear gain wider clinical acceptance it becomes important to establish how drugs are distributed in the ear as a function of time and for different delivery methods.
  
  
  METHODS
  The time course of gentamicin concentration in the inner ear fluids was simulated with a program that considered general pharmacokinetic principles and incorporated inner ear dimensions and drug dispersal processes, including diffusion, clearance, and intercompartmental exchange.
  
  
  RESULTS
  Cochlear fluid space dimensions of the chinchilla were derived from three-dimensional magnetic resonance images and were incorporated into the simulator. The published time course of gentamicin in vestibular perilymph of chinchillas was closely approximated by the adjustment of parameters defining round window membrane permeability, clearance, and interscala exchange. To simulate the time course, it was necessary for drug entry into the vestibule to be dominated by interscala exchange rather than longitudinal spread through the helicotrema. The effects of different round window delivery methods were also calculated. Perilymph drug levels and spatial distribution in the ear were shown to be markedly influenced by the time the applied drug remained in the middle ear.
  
  
  CONCLUSIONS
  The development of local inner ear drug application strategies requires consideration of inner ear pharmacokinetic characteristics, delivery methods, and therapeutic range of the drug.
authors.affiliation: Tübingen Hearing Research Center, University of Tübingen, Germany.
authors.forename: Stefan K R
authors.initials: SK
authors.lastname: Plontke
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Wood
authors.forename: Alec N
authors.initials: AN
authors.lastname: Salt
mesh_terms: D000818:Animals; D001682:Biological Availability; D002463:Cell Membrane Permeability / Q000502:physiology; D002682:Chinchilla; D003198:Computer Simulation; D004058:Diffusion; D004710:Endolymph / Q000378:metabolism*; D005839:Gentamicins / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008657:Metabolic Clearance Rate / Q000502:physiology; D010498:Perilymph / Q000378:metabolism*; D012405:Round Window, Ear / Q000378:metabolism; D012533:Scala Tympani / Q000378:metabolism; D012984:Software
chemical_list: D005839:Gentamicins