How Mexican Cartels Test Fentanyl on Vulnerable People and Animals NYT > Top Stories Natalie KitroeffοΌ Paulina Villegas and Meridith Kohut 26 December 2024 at 05:00 A global crackdown on fentanyl has led cartels to innovate production methods and test their risky formulas on people, as well as rabbits and chickens.