Cyclopentylfentanyl is an opioid pain reliever structurally related to fentanyl, which has been available on the internet as a designer drug, primarily in Sweden and other Nordic countries.

IUPAC name
CAS Number2088918-01-6
PubChem CID126682248
Chemical and physical data
Molar mass376.544 g·mol−1

Side effects

The side effects of fentanyl analogs closely resemble those of fentanyl itself, encompassing symptoms such as itching, nausea, and potentially life-threatening respiratory depression. Fentanyl analogs have claimed the lives of numerous individuals across Europe and the former Soviet republics, with the most recent resurgence observed in Estonia in the early 2000s, and the emergence of novel derivatives continues to be a concern.

A fresh wave of fentanyl analogs and the associated fatalities emerged around 2014 in the United States and has continued to gain prominence. Mainly since 2016, these substances have been responsible for hundreds of overdose-related deaths on a weekly basis.

Legal Status:

Cyclopentylfentanyl was prohibited in Sweden in January 2017.

In the United States, Cyclopentylfentanyl has been classified as a Schedule I controlled substance since February 1, 2018.


  • What is Cyclopentylfentanyl?
  • Cyclopentylfentanyl is a synthetic opioid analgesic. It is structurally similar to fentanyl and has been marketed and sold online as a designer drug.
  • What are the side effects of Cyclopentylfentanyl?
  • The side effects of Cyclopentylfentanyl are akin to those of fentanyl itself and may include itching, nausea, and, notably, the potential for severe respiratory depression, which can be life-threatening.
  • How has the use of Fentanyl analogs impacted Europe and the former Soviet republics?
  • The use of fentanyl analogs has led to numerous fatalities across Europe and the former Soviet republics, with a resurgence in Estonia in the early 2000s. New derivatives of these drugs continue to emerge.
  • When did the surge of fentanyl analogs and associated deaths begin in the United States?
  • A new wave of fentanyl analogs and the associated increase in fatalities began around 2014 in the United States. Since 2016, these substances have been responsible for hundreds of overdose-related deaths every week.
  • What is the legal status of Cyclopentylfentanyl in Sweden?
  • Cyclopentylfentanyl was made illegal in Sweden in January 2017.
  • Is Cyclopentylfentanyl legal in the United States?
  • No, Cyclopentylfentanyl is classified as a Schedule I controlled substance in the United States, a designation it has held since February 1, 2018.
  • What precautions should one take regarding Cyclopentylfentanyl?
  • It is essential to recognize that Cyclopentylfentanyl is a potent and dangerous substance. Its use can have severe health consequences, and it is strongly discouraged. If you encounter it or suspect its use, it should be reported to the appropriate authorities.
  • Where can individuals seek help for opioid-related issues or addiction?
  • If you or someone you know is dealing with opioid-related issues or addiction, it is vital to seek professional help immediately. Addiction treatment centers, healthcare providers, and addiction helplines are valuable resources for guidance and support in overcoming opioid addiction.


  1. Helander A, Bäckberg M, Signell P, Beck O (2017): “Incidents Involving Acrylfentanyl and Other Innovative Designer Fentanyls – Findings from the Swedish STRIDA Project.” Published in Clinical Toxicology. Volume 55, Issue 6, pages 589–599. doi: 10.1080/15563650.2017.1303141. PMID: 28349714. S2CID: 11978059.
  2. Zawilska JB (2017): “An Expanding World of Novel Psychoactive Substances: Opioids.” Appeared in Frontiers in Psychiatry. Volume 8, page 110. doi: 10.3389/fpsyt.2017.00110. PMC: 5492455. PMID: 28713291.
  3. Jane Mounteney; Isabelle Giraudon; Gleb Denissov; Paul Griffiths (July 2015): “Fentanyls: Are we missing the signs? Highly potent and on the rise in Europe.” Published in the International Journal of Drug Policy. Volume 26, Issue 7, pages 626–631. doi: 10.1016/j.drugpo.2015.04.003. PMID: 25976511.
  4. Armenian P, Vo KT, Barr-Walker J, Lynch KL (2017): “Fentanyl, Fentanyl Analogs, and Novel Synthetic Opioids: A Comprehensive Review” (PDF). Found in Neuropharmacology. Volume 134 (Part A), pages 121–132. doi: 10.1016/j.neuropharm.2017.10.016. PMID: 29042317. S2CID: 21404877.
  5. “Five New Substances Classified as Narcotics. Published on January 25, 2017.”
  6. “Schedules of Controlled Substances: Temporary Placement of Seven Fentanyl-Related Substances in Schedule I.” Published in the Federal Register on February 1, 2018.

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