Or phrased another way—why doesn’t your whole body get a little numb when you take a painkiller? Let’s limit this discussion to what are called nonsteroidal drugs, like ibuprofen. Ibuprofen, and other drugs like it, work by interrupting the series of signals that your body uses to communicate pain to your brain. The COX (cyclooxygenase) family of enzymes play an important, but intermediate, role in this pathway. This means that the COX enzymes take one type of signal and convert it into another that your body recognizes as pain. By working on an intermediate messenger, ibuprofen only takes effect where the pain is occurring—that first signal has to already be there—so your whole body doesn’t get numb when you take ibuprofen.