A medication cartridge plunger including a sealing member, which is formed of a resilient material, and a force distributing member, which is attached to sealing member and formed of a material more rigid than the resilient material. The force distributing member is shaped complementary with the sealing member to distribute to the sealing member a medication expelling force that may be applied to the force distributing member by an external drive element to drive the plunger forward. The force distributing member includes a radial periphery fit within a hollow of the sealing member. The radial periphery has a plurality of apex regions connected by spanning regions, which apex regions are disposed along a common circle centered on an axial center of the medication cartridge plunger. The spanning regions are disposed within the common circle, and each apex region, relative to the common circle, is not in diametric alignment with any of the other apex regions.
