Phenampromide is an opioid analgesic from the ampromide family of drugs, related to other drugs such as propiram and diampromide. It was invented in the 1960s by American Cyanamid Co. Although never given a general release, it was research found that 60 mg of phenampromide is equivalent to about 50 mg of codeine. Tests on its two enantiomers showed that all of the analgesic effects were caused by the (S)-isomer. Introduction of a phenyl group to the 4-position of the piperidine-ring produces a drug 60-fold more potent than morphine. The most potent reported derivative is 4-hydroxy-4-phenyl phenapromide which displays analgesic activity some x150 greater than morphine.The fentanyl analogue 4-phenylphenampromide