A surgical device for injecting a chemical agent within a subject for use in endoscopic injection therapies is disclosed. The device includes a support body, a motion transmitting unit, an agent delivery system and a guide housing. The motion transmitting unit is movable relative to the support body. The agent delivery system includes a needle for extending into a subject and structure defining a conduit between the support body and the needle. The guide housing has a flexible elongated body, an internal elongated passage and friction reducing material lining the passage. At least a portion of the motion transmitting unit adjacent the needle is slideably housed within the guide housing. The device offers a surgeon improved ease of needle extension and retraction when the distal end of the endoscope is bent at acute angles.