A substance delivery device that includes a hypodermic needle with a tube for receiving and containing a volume of a substance. The substance delivery device includes a rod, a portion of which is of a size and shape to fit within the tube of the hypodermic needle. The rod can be displaced into and within the tube to contact and apply a force to a volume of substance contained within the tube to cause, at least in part, the volume of substance to be discharged out of the tube. The substance delivery device includes a rod displacement mechanism that applies a force to the rod to cause the rod to be displaced into and within the tube. The substance delivery device also includes a needle retraction mechanism that is configured to apply a force to the hypodermic needle to cause the hypodermic needle to retract from within a patient.
