A syringe assembly having a barrel for containing one or more medicaments and a stopper disposed in the barrel defining and separating a first volume and a second volume within the syringe assembly. The stopper includes a permanent seal fluidly sealing the stopper to the barrel about the entire perimeter of the stopper intermediate the first volume and second volume, and a channel bypassing the permanent seal, the channel having a first opening in fluid communication with the second volume and a second opening selectively sealed from the first volume by a resilient seal. The resilient seal is moveable between a sealing configuration and an open configuration to selectively seal the channel from the first volume and is moveable from the sealing configuration to the open configuration upon fluid pressure in the first volume or second volume exceeding a first pressure threshold.