An analgesic is a drug used for relief of pain. Analgesics mainly impair perception of or emotional response to pain by action on the higher brain centers. Aspirin and paracetamol are mild but effective. Phenylbutazone, indomethacin,and ibuprofen are, like aspirin, useful in treating rheumatoid arthritis by reducing inflammation as well as relieving pain. Narcotic analgesics derived from opium alkaloids range from the milder codeine and dextropropoxyphene, suitable for general use, to the highly effective euphoriant and addictive morphine and heroin. These are reserved for severe acute pain and terminal disease, where addiction is either unlikely or unimportant. Pethidine (demerol) is an intermediate narcotic.