The present invention provides methods and devices for controlled delivery of a therapeutic agent to an internal cavity of the ear, particularly to the inner ear. In general, the invention uses a drug delivery unit for inner ear treatment which employs a portion of carrier media material containing one or more therapeutic agents therein. The carrier media material is designed to release the therapeutic agents in a controlled manner over time. The drug delivery unit is shaped and sized for placement of at least a portion thereof in the round window niche of a patient. The released therapeutic agents come in contact with the round window membrane and pass therethrough into the inner ear for treatment purposes. This system provides many benefits ranging from the ability to deliver drugs in a site specific, highly controlled manner to the transfer of such materials with minimal patient discomfort and monitoring requirements.