A drug delivery system to deliver two or more medicaments operable through a auto-injector drug delivery device and a single dispense interface. The device comprises a housing defining a primary reservoir containing a first medicament. A dosing mechanism operably connected to the primary reservoir. A single dispense interface is configured for fluid communication with the primary reservoir and a secondary reservoir of medicament containing at least one drug agent configured for fluid communication to the single dispense interface. A single activation of the dosing mechanism causes medicament from the primary reservoir and a non-user settable dose of the second medicament to be expelled through the single dispense interface.