Once people realized that opioid drugs could cause addiction and deadly overdoses, they tried to use newer forms of opioids to treat the addiction to its parent. Morphine, about 10 times the strength of opium, was used to curb opium cravings in the early 19th century. Codeine, too, was touted as a nonaddictive drug for pain relief, as was heroin.
Those attempts were doomed to failure because all opioid drugs interact with the brain in the same way. They dock to a specific neural receptor, the mu-opioid receptor, which controls the effects of pleasure, pain relief and need.