In the search for opioid analgesics with less abuse potential, a number of semi-synthetic opiates were developed. These substances are referred to as mixed agonist-antagonists analgesics. Nalbuphine (Nubain) belongs to this group of substances. It was approved for marketing in the United States in 1979 and remains as the only opioid analgesic of this type (marketed in the U.S.) not controlled under the Controlled Substances Act (CSA). When the Controlled Substances Act (CSA) was enacted in 1971, nalbuphine was placed in schedule II. Endo Laboratories, Inc. subsequently petitioned the DEA to exclude nalbuphine from all schedules of the CSA in 1973. After receiving a medical and scientific review and a scheduling recommendation from the Department of Health, Education and Welfare, forerunner to the Department of Health and Human Services, nalbuphine was removed from schedule II of the CSA in 1976. Presently, nalbuphine is not a controlled substance under the CSA. Kentucky has controlled nalbuphine in schedule IV of state law.