Tolerance and dependence to opiates.

In the 19th century, investigators recognized that addiction to opiates involves tolerance and dependence. In the United States, the National Academy of Sciences and the Public Health Service initiated systematic investigations into opiate addiction in 1929. Tolerance and dependence to morphine, the prototype for opiate drugs, were the emphasis of human studies for the next fifty years. This presentation highlights salient features of tolerance and dependence learned in these studies and relates these findings to clinical use in treating pain.