A flexible container is provided for the storage and mixing together of diluents and medicaments. The container incorporates multiple compartments, separated by peelable seals, in which the diluents and medicaments are stored. The container is constructed of thermoplastic materials having high oxygen and moisture barrier properties which allows the container to be stored for extended periods of time without degrading the contents. The seals are ruptured by manipulation of the container to thereby mix the contents together for delivery through standard IV arrangement to a patient. The seals are constructed to provide a non-linear resistance characteristic to hydraulic pressure, which causes the seal to peel open completely along its length. The container is folded-over along the line of one of the seals and also includes a locking tab and retaining slot to secure the bag in a folded-over condition.