Patent ID: 8449499

Claim:
A method for selecting a dose of medication, the method comprising: compressing a plunger assembly into a barrel assembly, wherein the plunger assembly includes a shaft having a distal end and a proximal end; rotating the plunger assembly within the barrel assembly to select a dosage by viewing visual indicia indicative of the dosage; inserting the barrel assembly into a fluid; releasing the plunger assembly such that a force producing element produces a force on the plunger assembly; the force producing element extracting the plunger assembly from the barrel assembly until a radial rib contacts a detent on a barrel cap assembly, wherein the radial rib is disposed between two or more lengthwise ribs; wherein the radial rib is disposed in at least one portion of a circumference of the shaft, but not extending along a full circumference of the shaft; and wherein the radial rib is disposed lengthwise on the shaft between the distal end and the proximal end of the shaft to provide a predetermined volume of the fluid in the barrel assembly when the radial rib contacts the barrel cap assembly; and siphoning the fluid into the barrel assembly as the plunger assembly is extracted.