Abstract: A medication cartridge for use with a medication delivery pen having a cartridge body with threads at its distal end for receiving a pen-needle. The threads are either integrally molded in the cartridge or on the outer surface of a cap used to retain a septum on the distal end of the cartridge body. The cartridge body of the medication cartridge also includes threads or a snap-ring at its proximal end for attaching the medication cartridge directly to a pen body housing of the medication delivery pen without the need for a medication cartridge holder.

Abstract: An operable syringe assembly comprises a barrel including a cylindrical coextruded body portion having a longitudinal axis. The body portion forms a side wall spaced from the axis defining a chamber for retaining fluid. The body portion includes an open proximal end and a distal end and further includes an inner portion of plastic material and a rigid portion of plastic material surrounding the inner portion. The rigid portion has a higher hardness than the inner portion. A plunger including an elongate shaft portion having a proximal end, a distal end and a rigid piston at the distal end is provided. The piston has an outside diameter greater than the inside diameter of the inner portion and a higher hardness than the inner portion. The piston portion is slidably positioned in fluid-tight engagement inside the barrel. The fluid-tight engagement is caused by the piston compressing the inner portion of the plastic material of the coextruded body portion.