A needle assembly comprises a body configured for attachment to a drug delivery device. The body defines a cavity. A septum is positioned within the cavity and a stopper positioned within the cavity such that the cavity, septum, and stopper define a reservoir. A double ended needle is positioned in the stopper and septum, the needle comprising a proximal end and a distal end. A release mechanism is positioned near a distal end of the body. A biasing element is positioned to drive the stopper. During a dose dispensing step, the release mechanism drives the proximal end of the needle out of the septum so that the proximal end resides in said reservoir. The biasing element may also drive the stopper proximally.
