Painkillers have a small family tree. Most of the used, and sometimes abused, pain medications available have roots in either the willow tree or the poppy. Aspirin, originally derived from willow bark or other plant extracts, works on the same molecular pathways as medications with more recent origins, including the crop of highly targeted COX-2 inhibitors. And researchers time and again returned to the opium poppy to derive effective, often addictive, painkillers such as codeine, oxycodone, and fentanyl. Researchers are taking new approaches to understand and combat chronic pain (see Gains in Pain Research), but little has changed in 5,000 years. These two time lines depict the histories for these major drug classes.
--Compiled by Brendan A. Maher
