A drug delivery system that can be deployed from a catheter and retained within the bladder for delivery of treatment drug solutions over a period of time. The delivery system includes an inflatable or expandable delivery element that can be collapsed within the catheter tip for navigation into the bladder before being inflated or expanded within the bladder. The inflated or expanded delivery element can engage the bladder walls or sized to be too large to be passed from the bladder such that the delivery element is retained within the bladder after inflation or expansion to administer a treatment drug solution over an extended period of time.
