Isobutyryl Fentanyl Safety Data Sheet (PDF 5 pages):
https://www.caymanchem.com/msdss/18584m.pdf

Isobutyryl Fentanyl Monograph (PDF 5 pages):
http://www.swgdrug.org/Monographs/Isobutyryl%20fentanyl.pdf

An opioid analgesic that is an analog of fentanyl and has been sold online as a designer drug. It is believed to be around the same potency as butyrfentanyl but has been less widely distributed on illicit markets, though it was one of the earliest of the "new wave" of fentanyl derivatives to appear, and was reported in Europe for the first time in December 2012.