Gentamicin Concentration Gradients in Scala Tympani Perilymph following Systemic Applications

ST. The absolute gentamicin concentrations increased with the amount of drug applied and time before sampling. While it is likely that the basal-apical gradient measured after local drug applications to the round window niche is the result of the direct uptake of drugs into the perilymph of the ST, dis-tribution by diffusion and a very low perilymph flow towards the cochlear apex, computer simulations suggested that the apical-basal gradient observed with these systemic applica-tions can be explained by higher entry rates of gentamicin in the apex compared to the basal turns of the cochlea. It is also possible that gentamicin enters perilymph indirectly from the blood via the endolymph. In this case the faster ki-netics in apical turns could be due to the smaller cross-sec-tional area of ST relative to endolymph in the apical turns. © 2013 S. Karger AG, Base