injecting a therapeutic fluid comprising dexamethasone into a proximal port of an elongate fillable body that is axially aligned with a central lumen of a distal delivery shaft extending from a distal end of the elongate fillable body while the elongate fillable body is positioned entirely external to a tympanic membrane of an ear, the distal delivery shaft having a smaller diameter than an outer diameter of the elongate fillable body and the central lumen of the distal delivery shaft being filled entirely by the therapeutic fluid, wherein the elongate fillable body has a longitudinal length extending from the proximal port to the distal end that is greater than a maximum lateral width of the elongate fillable body and that is smaller than a longitudinal length of the distal delivery shaft; and

after injection into the proximal port axially aligned with the central lumen of the distal delivery shaft extending from the distal end of the elongate fillable body, delivering the therapeutic fluid comprising dexamethasone from the distal end of the elongate fillable body and through the distal delivery shaft that is positioned through the tympanic membrane and to a distal-most outlet adjacent to a round window niche of a cochlea such that about 5 μL to about 500 μL of the therapeutic fluid comprising dexamethasone is deposited into the round window niche, wherein the therapeutic fluid comprising dexamethasone deposited into the round window niche comprises a gel composition for sustained release of the dexamethasone.