A plastic container containing a pharmaceutical composition comprising benzoic acid or a derivative or a pharmaceutically acceptable salt thereof and a COX-inhibitor of the oxicam-type or a pharmaceutical acceptable salt thereof, wherein the container material selected from one or more members of the group consisting of a homopolymer of polypropylene (PP), a copolymer of polypropylene (PP), a homopolymer of polyethylene terephthalate (PET) and a copolymer of polyethylene terephthalate (PET), and optionally one or more non-polymeric components.