A syringe includes a barrel with a plunger movably inserted therein and a tube extends from a first end of the barrel and is in communication with a passage in the barrel. A flange extends inward from an inner periphery of the tube. A stopper is connected to the plunger and a rod extends from the plunger and through the stopper. The rod includes engaging protrusion which is engaged with the flange to prevent the plunger from being pulled back when the plunger is pushed into the barrel after injection. The rod includes a groove and the plunger can be broken at the groove.