Abstract: A device for releasing active ingredient into a liquid flow passing through a system for parenteral application of the ingredient comprises a receptacle composed of two half shells. The receptacle is subdivided by a ribbed aluminium foil into two chambers and has an inlet at its upper end and an outlet at its lower end. The two chambers have vent means at their upper ends. One of the chambers contains two overflows a first one of which empties into the outlet while the second one empties into the other chamber. In the latter chamber there is present a further overflow which also empties into the outlet, as well as a plate-shaped carrier charged with the active ingredient to be released. The liquid flows from the inlet via the first chamber and the second overflow therein into the other chamber and from there upwardly past a carrier charged with active ingredient, and onward via a third overflow in the other chamber into the outlet.