Kit for use in a treatment of administering at least one pharmaceutically active substance by PAT (pressurized aerosol therapy) in a hollow organ or in a body cavity, of a patient, comprising: (a) a sterile and closed prefilled drug containing device system for use in administering at least one pharmaceutically active substance by PAT in a hollow organ or in a body cavity of a patient, comprising a flexible package (100, 101), comprising: - at least one container comprising at least one pharmaceutically active substance in powder, lyophilisate, solution, liquid, gel or suspension or emulsion form, and being provided with breakable, an openable, or perforable cap; and - a bag of liquid diluent, connectable to an aerosol generating means, for use with an application lance and/or injection lance with nozzle, ∘ wherein the liquid diluent is a physiologically acceptable aqueous diluent; ∘ and wherein the bag is equipped with a mixing tube; and wherein said package (100, 101) comprises at least one flexible airtight sterile casing, containing said container, and said perforation device; and wherein the said container is manually maneuverable from the outside of the casing in order to be opened inside the closed casing; and whereupon after opening of the said container and of the said closure, and selectively mixing by dissolving or reconstituting the at least one pharmaceutically active substance with the liquid diluent through the mixing tube, a solution of the at least one pharmaceutically active substance in the liquid diluent is provided for administering by PAT in a hollow organ or in a body cavity of a patient; and (b) an application lance and/or injection lance with nozzle; and/or (c) a pumping system, preferably a micro-pump, for use with an application lance and/or injection lance with nozzle for use in administering the at least one pharmaceutically active substance by PAT in a hollow organ or in a body cavity of a patient. (a) a sterile and closed prefilled drug containing device system for use in administering at least one pharmaceutically active substance by PAT in a hollow organ or in a body cavity of a patient, comprising a flexible package (100, 101), comprising: - at least one container comprising at least one pharmaceutically active substance in powder, lyophilisate, solution, liquid, gel or suspension or emulsion form, and being provided with breakable, an openable, or perforable cap; and - a bag of liquid diluent, connectable to an aerosol generating means, for use with an application lance and/or injection lance with nozzle, ∘ wherein the liquid diluent is a physiologically acceptable aqueous diluent; ∘ and wherein the bag is equipped with a mixing tube; and wherein said package (100, 101) comprises at least one flexible airtight sterile casing, containing said container, and said perforation device; and wherein the said container is manually maneuverable from the outside of the casing in order to be opened inside the closed casing; and whereupon after opening of the said container and of the said closure, and selectively mixing by dissolving or reconstituting the at least one pharmaceutically active substance with the liquid diluent through the mixing tube, a solution of the at least one pharmaceutically active substance in the liquid diluent is provided for administering by PAT in a hollow organ or in a body cavity of a patient; and - at least one container comprising at least one pharmaceutically active substance in powder, lyophilisate, solution, liquid, gel or suspension or emulsion form, and being provided with breakable, an openable, or perforable cap; and - a bag of liquid diluent, connectable to an aerosol generating means, for use with an application lance and/or injection lance with nozzle, ∘ wherein the liquid diluent is a physiologically acceptable aqueous diluent; ∘ and wherein the bag is equipped with a mixing tube; and wherein said package (100, 101) comprises at least one flexible airtight sterile casing, containing said container, and said perforation device; and wherein the said container is manually maneuverable from the outside of the casing in order to be opened inside the closed casing; and ∘ wherein the liquid diluent is a physiologically acceptable aqueous diluent; ∘ and wherein the bag is equipped with a mixing tube; and wherein said package (100, 101) comprises at least one flexible airtight sterile casing, containing said container, and said perforation device; and wherein the said container is manually maneuverable from the outside of the casing in order to be opened inside the closed casing; and (b) an application lance and/or injection lance with nozzle; and/or (c) a pumping system, preferably a micro-pump, for use with an application lance and/or injection lance with nozzle for use in administering the at least one pharmaceutically active substance by PAT in a hollow organ or in a body cavity of a patient.