An unfamiliar name is starting to appear in alerts issued by state coroner's offices, local law enforcement, and college campuses: Cyclorphine.
This synthetic opioid has been linked to at least 122 deaths in the United States since July 2025. In April, the Office of National Drug Control Policy classified it as an “emerging drug threat.”
In August, the US Drug Enforcement Administration temporarily classified cyclorphine as a Schedule I controlled substance, making it illegal in the United States.
But experts do not expect it to become a problem as widespread or as serious as other types of illicit opioids. Here's what you should know about cyclorphin.
What is cyclorphin and how did it appear?
Cyclorphine belongs to a relatively new class of opioids called orphins, which have not previously been used for medical purposes, according to Dr. Naron Dasgupta, a researcher who specializes in studying the illicit drug market, its composition, and its effects at the University of North Carolina at Chapel Hill. He said that cases of cyclorphine appearing in the United States are still “sporadic, and its detection is much less than the detection of samples of fentanyl.”
Researchers at the university examined the drug for the first time in the United States in August 2024, according to Dasgupta, who pointed out that his colleagues in Europe have been monitoring orphins since 2019, and have been following the possibility of this class of drugs appearing in the United States since then.
He explained that the emergence of cyclorphine in the United States is also linked to countries around the world banning fentanyl analogues, which prompted the illicit markets to create drugs that are not related to fentanyl, but which produce the same effects on their users.
Dasgupta was not surprised by his appearance. Cyclorphin has been detected in about 25 US states, according to Dr. Alex Krotulski, director of the toxicology and chemistry divisions at the Center for Forensic Science Research and Education.
In the Midwest, including Illinois and Tennessee, the drug appears in powder form, often mixed with fentanyl and heroin. In the South, including Texas, Louisiana, and Alabama, it has been observed in the form of grains.
How strong is cyclochlorphine?
Laboratory models show that cyclorphene is more effective than fentanyl, which is consistent with what researchers have observed in humans, Krotulski says.
Due to its intensity, a small amount is enough to have a greater effect.
Health effects of cyclorphin
As an opioid, cyclorphine affects the body's opioid receptors, which can lead to respiratory depression, which means it slows or stops, said Dr. Shravani Durbhakula, director of comprehensive pain services at Vanderbilt University.
It may also cause:
The effects of an overdose can be reversed with naloxone, a medication used to treat opioid overdoses, also known as Narcan.
Durbhakula said that the cases she dealt with often witnessed cyclorphine being mixed with other substances, even in counterfeit pills for drugs such as Xanax and OxyContin, which increases the strength of its effect and its danger.
She added: “It was also found alone, so this does not mean that it is always mixed with other substances. But it is clear that mixing it with other substances makes it more deadly.”
Detection of cyclorphin
Fentanyl test strips don't detect cyclorphine because they are two different substances, said Dr. David Liss, an assistant professor of emergency medicine at the University of Washington.
He explained that the usual tests in hospitals do not include this drug, and detecting it may require requesting specialized tests.
"I don't think there's any way to test it on an individual level," Lees added.
He added that he also believes the number of cases linked to these new compounds is lower than the actual number, as hospitals cannot identify orphine opioids, and it is not clear whether other laboratories test them regularly.
What is the future of cyclorphin?
Krotolski expects that the prevalence of cyclophene will decline “very quickly, after it was listed among the controlled substances by the US Drug Enforcement Administration and in China, which is the source of many of the new opioids. The number of cases associated with it is likely to decrease, and it will appear in sporadic cases in the future.
But Krotolski pointed out that cyclorphine is only one of at least 100 types of opioids that have been observed to appear over the past decade, and he expects that new types will emerge in the future.
He said: "For example, we will not talk about cyclorphine next October, but rather about the newest types of opioids that will appear, and there may be three or four new types by then."
