A cap system for sealing injectable drugs within a vial is disclosed. The system includes an elastomeric stopper, a retainer member, a locking member, a cap assembly and a piercing member. The retainer member is arranged to snap onto the vial and the locking member slid with respect to the retainer member to permanently seal the vial. The cap assembly includes a cap and a band and is coupled to the locking member. The cap releasably holds the piercing member. The band is arranged to be removed to enable the cap to move the piercing member to penetrate the stopper, whereupon the cap can be removed. The piercing member is arranged to be connected to a syringe or other instrument to withdraw the vial's contents.