A catheter body includes a main lumen and an auxiliary lumen. The main lumen has an outlet opening located at a distal end of the body and an inlet opening at a proximal end. The auxiliary lumen has an outlet opening located behind and spaced from the distal end a distance of 5-10 cm and an inlet lateral opening located toward the proximal end. An adapter for providing inlet ports communicating with the inlet openings of the main lumen and auxiliary lumen is provided on the catheter body. The adapter includes three members detachably connected to one another. The forward and middle members have threaded portions which engage one another and the middle and rearward members also have threaded portions which engage with one another. Annular seals are provided between the forward and middle members and the middle and rearward members. The adapter can be readily attached to the catheter body and an external device for dosing a liquid medicine can be attached to the adapter.