Not sure if I understand your point. There are a number of medical devices that are liquids. For example, there are spray-on skin barriers to prevent wounds due to urine that are regulated as medical devices. AC5 is dispensed as a liquid and forms a physical barrier. It does does not require chemical action or effect on the body nor is it metabolized in the production of its primary intended effect; the barrier seal formed apparently produces the effect. See the FDA definition on web of a medical device for the precise language.