cyclopentylfentanyl cyclopentylfentanyl cyclopentylfentanyl is an opioid analgesic that is an analog of fentanyl and has been sold online as a designer drug, mainly in sweden and other scandinavian countries. cyclopentylfentanyllegal statuslegal status ca: schedule i de: npsg (industrial and scientific use only) uk: class a us: schedule i illegal in sweden identifiers iupac name n-phenyl-n-cyclopentanecarboxamide cas number2088918-01-6pubchem cid126682248chemspider81367208unii79ny29l78cchemical and physical dataformulac25h32n2omolar mass376.544 g·mol−13d model (jsmol)interactive image smiles c1ccc(c1)c(=o)n(c2ccn(cc2)ccc3=cc=cc=c3)c4=cc=cc=c4 inchi inchi=1s/c25h32n2o/c28-25(22-11-7-8-12-22)27(23-13-5-2-6-14-23)24-16-19-26(20-17-24)18-15-21-9-3-1-4-10-21/h1-6,9-10,13-14,22,24h,7-8,11-12,15-20h2key:peasfkspituzgt-uhfffaoysa-n side effects 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. a new wave of fentanyl analogues and associated deaths began in around 2014 in the us, and have continued to grow in prevalence; especially since 2016 these drugs have been responsible for hundreds of overdose deaths every week. legal status cyclopentylfentanyl was made illegal in sweden in january 2017. cyclopentylfentanyl is a schedule i controlled drug in the usa since 1 february 2018.