thiofentanyl thiofentanyl thiofentanyl is an opioid analgesic that is an analogue of fentanyl. not to be confused with thiafentanil. thiofentanylclinical datapregnancycategory c atc codenonelegal statuslegal status au: s9 (prohibited substance) ca: schedule i de: anlage i (authorized scientific use only) uk: class a us: schedule i identifiers iupac name n-phenyl-n-propanamide cas number1165-22-6 npubchem cid62380chemspider56168 yunii954535y32ychebichebi:61099 ycomptox dashboard (epa)dtxsid00151400 chemical and physical dataformulac20h26n2osmolar mass342.50 g·mol−13d model (jsmol)interactive image smiles o=c(cc)n(c1ccn(ccc2=cc=cs2)cc1)c3=cc=cc=c3 inchi inchi=1s/c20h26n2os/c1-2-20(23)22(17-7-4-3-5-8-17)18-10-13-21(14-11-18)15-12-19-9-6-16-24-19/h3-9,16,18h,2,10-15h2,1h3 ykey:ymrfzdhydkzxpa-uhfffaoysa-n y ny (what is this?) (verify) thiofentanyl was sold briefly on the black market in the early 1980s, before the introduction of the federal analog act which for the first time attempted to control entire families of drugs based on their structural similarity rather than scheduling each drug individually as they appeared. thiofentanyl is made with the same synthetic route as fentanyl, but by substituting 2-(2-bromoethyl)thiophene for phenethyl bromide in the synthesis. 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.