A plurality of dosage-control members are detachably connected to the plunger rod of a multi-dose syringe along two opposing sides of the rod. Each dosage-control member has a cut in which the external diameter of the top rim of the syringe fits to prevent forward and reverse movement of the rod. Removal of one dosage-control member from one of the two opposing sides of the rod permits forward movement of the rod and plunger until the top rim snaps into the cut of another dosage-control member. Flexible salient arms extend obliquely from the rod in one-to-one correspondence with the dosage-control members to prevent reverse movement of the rod.