Drug delivery device and methods having a retaining member

A drug delivery device comprising:

• a housing comprising a cavity;
• a drug cartridge removably positioned in the cavity, the drug cartridge comprising a first plate having a channel with a drug pellet positioned therein, the drug cartridge comprising a second plate that is coupled to the first plate, the second plate comprising a first end including a first cantilever arm and an opposite second end including a cantilever arm, the cantilever arms being configured to effect an elastic occlusion of the channel, the first cantilever arm comprising a first planar surface and a first protrusion that extends outwardly from the first planar surface and the second cantilever arm comprising a second planar surface and a second protrusion that extends outwardly from the second planar surface, the protrusions being configured to at least partially occlude the channel at an occluding position such that the drug pellet cannot pass through the channel at the occluding positions without force, greater than that of gravity, applied to the drug pellet sufficient to deflect one of the cantilever arms an amount permitting passage of the drug pellet past one of the cantilever arms;
• and
• a push rod configured to be positioned through the channel to apply a force to the drug pellet sufficient to deflect the cantilever arms to expel the drug pellet from the channel.