Drug permeability of the endolymphatic sac

Intravenously injected kanamycin sulfate (KM) was located in the endolymphatic sac (ES) of guinea pigs by an immunohistologic method. Kanamycin sulfate had passed through the capillaries in the subepithelial layer and reached the epithelial layer as early as 1 minute after injection. The amount of KM in the epithelial layer gradually increased with time (until 30 minutes after injection). The KM also accumulated in floating cells in the ES. These results tend to indicate that the ES is rather easily permeable to systemically administered drugs, which readily get into the regional endolymph. In conclusion, much more attention should be paid to the ES and drug ototoxicity associated with drug therapy in the management of patients with inner ear disturbances.