Abstract: A closure structure for a two-compartment vial having a stopper sealingly seated within the neck opening of the vial, and a cap interconnected between the stopper and the vial neck. The stopper has a cylindrical portion which protrudes outwardly of the vial neck and is surrounded by a resilient sleevelike collet associated with the cap. The collet is mechanically axially interlocked to the stopper and, together with the cylindrical stopper portion, moves into the neck opening when the closure is urged toward the vial to activate the latter. A cammed or tapered relationship exists between the collet and the vial neck which increases the gripping of the stopper by the collet when they are moved into the neck opening.

Abstract: A closure structure for a two-compartment vial or container wherein a lyophilized medication is contained in one compartment and a solvent is contained in the other compartment. A displaceable, moisture-proof plug is removably disposed within a constriction between the two compartments. The closure structure includes a stopper which is partially inserted into the neck of the vial and a cap having a portion for fastening the cap to the vial neck. The cap has a cup portion of reduced diameter which snugly surrounds the protruding portion of the stopper and is disconnectible from the fastening portion in order to move with the protruding portion of the stopper into the neck of the vial under manually applied pressure. The cup portion is then removed so that the needle of a syringe can be inserted through the stopper to communicate with the interior of the vial.