An automatic blow-gun syringe which uses carbon dioxide gas as the injecting force is described. Upon striking the animal, carbon dioxide gas is released by the chemical combination of sodium bicarbonate (baking soda) and acid (vinegar), within the blow-gun syringe. The syringe has been used successfully with captive collared peccaries (Dicotyles tajacu). It has the advantages of longer stability, dependable gas expansion, reduction of drug loss, and consistent drug injection.