4-Fluoroisobutyrfentanyl

4-Fluoroisobutyrfentanyl

Legal status
Legal status	CA: Schedule I UK: Class A US: Schedule I
Identifiers
IUPAC name N-(4-Fluorophenyl)-N-[1-(2-phenylethyl)-4-piperidinyl]-isobutanamide
CAS Number	244195-32-2
PubChem CID	100974914
Chemical and physical data
Formula	C23H29FN2O
Molar mass	368.50 g·mol−1
3D model (JSmol)	Interactive image
SMILES CC(C)C(=O)N(C1CCN(CC1)CCC2=CC=CC=C2)C3=CC=C(C=C3)F
InChI InChI=1S/C23H29FN2O/c1-18(2)23(27)26(21-10-8-20(24)9-11-21)22-13-16-25(17-14-22)15-12-19-6-4-3-5-7-19/h3-11,18,22H,12-17H2,1-2H3 Key:OZDOSQNUJIXEOR-UHFFFAOYSA-N

4-Fluoroisobutyrylfentanyl (also known as 4-FIBF and p-FIBF) is an opioid analgesic that is an analog of butyrfentanyl and structural isomer of 4-Fluorobutyrfentanyl and has been sold online as a designer drug. It is closely related to 4-fluorofentanyl, which has an EC₅₀ value of 4.2 nM for the human μ-opioid receptor.

Side effects of fentanyl analogs are similar to those of fentanyl itself, which include itching, nausea and potentially serious respiratory depression, which can be life-threatening. Fentanyl analogs have killed hundreds of people throughout Europe and the former Soviet republics since the most recent resurgence in use began in Estonia in the early 2000s, and novel derivatives continue to appear.

4-Fluoroisobutyrylfentanyl is a Schedule I controlled substance in the United States. In the UK, it is a Class A drug. In Canada, it is a Schedule I drug.