Disclosed herein is a ready-to-use injection device for single use and a container for such device. The container comprises at least one first closed chamber for containine an active substance and optionally a second closed chamber for containing a quid substance comprising an active substance or a solvent. The two chambers are separated by a separation wall which is impermeable and breakable upon exertion of an external force, resulting in enhanced mixing of the substances contained in the device with a minimal formation of air bubbles. The present injection device is safe and particularly well suited for enhanced mixing of pharmaceutically active compositions to be injected in patients and can be used for vaccination programs.
