The story provides a figure depicting the structural formula of actual fentanyl, and next to it similar fentanyl-like molecules that are being trafficked.

Caption: "Yan Xiaobing was indicted for distributing these similar compounds; making slight changes to the molecular structure can have unpredictable effects on potency."

Also: [I]n recent years, rogue chemists have unearthed instructions for analogues that researchers discovered decades ago but never put into legitimate use.

While Chinese authorities control fentanyl, they’ve been slow to ban new analogues.