Powerful animal sedative likely cause of overdose spike in Chicago

A potent animal tranquilizer is likely behind an increase in drug overdoses in Chicago this month, health officials warned on Monday. 

The overdoses happened between May 11 and May 14, and drug samples from those cases tested positive for elevated levels of medetomidine. This powerful veterinary tranquilizer is not approved for human use. 

Chicago health officials said medetomidine has not previously been detected in Chicago.