Long considered safe and non-addictive, gabapentin is increasingly showing up in the bodies of people who overdose on heroin and prescription opioids, reports Pew’s Stateline.

Recently, gabapentin has started showing up in a substantial number of overdose deaths in hard-hit Appalachian states. The neuropathic (nerve-related) pain reliever was involved in more than a third of Kentucky overdose deaths last year.