The present invention provides devices and methods for mixing a formulation containing two or more constituents, such as a drug product and a diluent. The devices have a chamber for securing a container of the drug product. Various embodiments are presented. In one embodiment the device has two or more sides connected by a hinge, the two or more sides defining the chamber between them, and a handle for grasping and manipulating the device. In another embodiment the device has a housing with two or more side bars defining the chamber, the container being visible from outside the housing between the side bars and having a stopping element at the distal end, and a handle having two arms for grasping.