This article kind of blew my mind. There's an arms race happening with synthetic drugs added to paper, and thus nearly impossible to control.

No Pills or Needles, Just Paper: How Deadly Drugs Are Changing - The New York Times
https://www.nytimes.com/2026/03/21/world/deadly-drugs-paper.html

No Pills or Needles, Just Paper: How Deadly Drugs Are Changing

Lab-made drugs soaked into the pages of letters, books and even legal documents are being smuggled behind bars, killing inmates and frustrating investigators.

The New York Times