A drug mixing system including at least one receptacle port adaptor adapted tobe inserted into a port of a fluid receptacle, at least one syringe adaptoradapted to be attached to a syringe and to the at least one receptacle portadaptor and at least one vial adaptor adapted for connection to a vialcontaining a drug and adapted for connection to the at least one syringeadaptor, the system being characterized in that at least one of the receptacleport adaptor, the at least one syringe adaptor and the at least one vialadaptor being vented to the atmosphere in a manner which prevents release tothe atmosphere of possibly harmful contents of the vial in a liquid, solid orgaseous form.
