This disclosure relates to drug delivery devices, systems, and methods. In some aspects, a drug delivery device includes an elongate member defining a fluid passage and an opening in fluid communication with the fluid passage, and a projection extending radially from the elongate member. A portion of the elongate member extending axially from the projection to a distal end of the elongate member has a length sufficient to allow the distal end of the elongate member to reach subdermal tissue of a patient when the elongate member is inserted into the patient and the projection is in contact with an outer surface of skin of the patient, and the opening is positioned at a location along the elongate member such that the opening is disposed within a dermis of the patient when the elongate member is inserted into the patient and the projection is in contact with the outer surface of the skin of the patient.