While the structure of acetaminophen and ibuprofen are very different, the mode of action is similar. Both of these painkillers interfere with the COX family of enzymes we just talked about. Ibuprofen interacts more broadly with members of this family of enzymes, which ends up making it a good painkiller as well as a good antiinflammatory medication. Acetaminophen binds primarily to one of the members of this family (COX–2), so it’s basically just a painkiller.