Abstract: A single-use syringe is provided with a rod-like plunger having a plurality of frusto-conical ratchet teeth. A radially resilient locking spring clip having a circumferential opening, dangles on the ratchet teeth of the plunger. The original location of the spring clip on the plunger determines the maximum dosage which can be administered by the syringe. In use, a first withdrawal of the plunger allows medication to be drawn into the barrel of the syringe. The spring clip glides, by radial flexing, over the surface of the ratchet teeth during plunger withdrawal. The spring clip is maintained in relative position along the sidewall of the barrel by outwardly directed contact points which embed into the interior sidewall of the barrel. During administration of the medication previously drawn into the barrel, the spring clip moves along with the plunger since an interiorly directed camming tooth of the clip mechanically cooperates with the base of a ratchet tooth of the plunger.