Abstract: The invention relates to a release test system (10) for simulating the change in state of medical active ingredients in the region of a human or animal organ, comprising at least: a main body (12) of a release test vessel (16); a lid (14) of the release test vessel (16); technical control means (18) for influencing simulation conditions prevailing within the release test vessel (16), wherein the technical control means (18) comprise at least one stirring mechanism (20) and one temperature control device (22); and further comprising a sampling device (26). Provision is made for the lid (14) and at least the stirring mechanism (20) to be permanently connected to one another and for a nondetachable connection to be producible or to exist between the main body (12) and the lid (14).