Drug delivery devices include a flexible elongate body having a bladder end portion, a kidney end portion, and a drug lumen extending therebetween; and a drug reservoir which is located at the bladder end portion, contains a drug, and is defined at least in part by a semi-permeable wall. Methods include inserting the device into the ureter of a patient and permitting water in the bladder to diffuse through the semi-permeable wall to create an osmotic pressure to pump the drug through the drug lumen and out of the device at the kidney end portion and into the renal pelvis.