Remember when the term "designer drug" was used in the 1980s? One of the drugs included in that group was called 3-methylfentanyl, aka, mefentanyl. Although not widely used, it killed groups of people who tried it. Fast forward 4 decades and it's now one of the 30 fentanyl analogs that are responsible for the fentanyl crisis. And it's also one of the worst. What a difference a methyl group can make.
