A system for injecting DNA-based medications into humans is provided by the present invention. The system includes a needle-free injector (10) with an injection orifice of approximately 0.004 inches for supplying DNA-based medication at an initial pressure of from 3900 to 4300 psi, and then immediately declining to a level of about 2800 to 3800 psi, and then immediately cutting off pressure to terminate the injection. The injector includes an annular adapter (12) for spacing the injection orifice from the skin of the patient. The adapter includes an abutment (16) against which the injector is disposed so that the orifice is spaced approximately 0.76-1.0 inch from the skin of the patient, the adapter having an inner diameter at the distal end of approximately 0.50-0.70 inches. |