An adapter for disposition in a breathing system circuit between a source of breathable gas and a patient airway circuit, the adapter having: a tube with a side wall defining a breathing passage between a tube inlet and a tube outlet; an injector conduit extending laterally through the tube side wall having: a bore; a nozzle communicating between the bore and the passage; and an external port, where the port includes: syringe connector means for releasably sealing between the bore of the injector conduit and a syringe; and multiple dose inhaler connector means for releasably connecting the bore of the injector conduit and a multiple dose inhaler.