Cychlorphine: Dangers and How to Protect Yourself

Cychlorphine (N-propionitrile chlorphine) is a new synthetic opioid turning up in counterfeit pills and powders, and fentanyl test strips do not detect it. It is not a fentanyl. It belongs to a separate chemical family called the orphines, related to brorphine, and it has been linked to overdose deaths across the US, Canada and the UK since late 2024. Naloxone (Narcan) still reverses it. The two things that protect you most are knowing that a negative strip does not clear a sample, and never using alone.

Quick answers

What is cychlorphine? A lab-made opioid from the benzimidazolone (“orphine”) class. It acts on the same mu-opioid receptor as fentanyl and heroin, so it causes the same deadly effect: breathing slows and stops.

Will a fentanyl test strip catch it? No. Strips are built to recognize the fentanyl molecule, and cychlorphine has a completely different shape.

Does Narcan work on cychlorphine? Yes, as far as current evidence shows. The one published hospital case with lab-confirmed cychlorphine responded to naloxone. Give it, and give a second dose if breathing does not return in 2 to 3 minutes.

How strong is it? Early lab data suggest roughly 10 times fentanyl’s potency at the receptor, but that figure has not yet been published in a peer-reviewed paper. Treat it as “at least as dangerous as fentanyl.”

Where is it showing up? In powders and in fake Xanax, Percocet, OxyContin and Dilaudid tablets, often mixed with benzodiazepines, fentanyl, nitazenes or stimulants.

Where cychlorphine came from

The orphine family traces back to pharmaceutical research in the 1960s and 70s. Brorphine was the first to reach street markets, in 2020, and was placed under international control in 2022. Cychlorphine was first identified by the Center for Forensic Science Research and Education (CFSRE) in mid-2024.

It spread fast after China put nitazenes under blanket control in July 2025. CFSRE’s January 2026 public alert reported that as nitazene detections dropped, orphine detections rose, led by cychlorphine. At that point it had been confirmed in 25 fatal overdoses at CFSRE, from nine US states and three Canadian provinces, with more than 100 more tentative cases at NMS Labs. In 11 of those 25 deaths it was the only opioid found.

By May 2026, the UN Office on Drugs and Crime counted 10 countries reporting it, 182 drug seizures and 78 deaths in the US and UK. A Paris drug checking service found it in France in a sample that contained nothing else psychoactive (PMID 41507112).

Why it is so dangerous

It is an opioid you did not know you were taking. In the first published hospital case, a woman in her 20s took what she believed was alprazolam (Xanax). She was found unresponsive and not breathing adequately. Her initial urine drug screen was negative for opiates and fentanyl, and only advanced lab testing identified cychlorphine, alongside the designer benzodiazepine bromazolam (PMID 42481906). That case is the pattern to worry about: a fake pill, no opioid tolerance, and a routine test that finds nothing.

The first population data show the same mismatch at scale. In a 2026 urine toxicology study of 112 people who inject drugs in Estonia, a third said they had used fentanyl, nitazenes or other synthetic opioids, but lab testing rarely confirmed that. Instead, half of them had cychlorphine in their urine, and nearly one in five participants overall tested positive for it (PMID 42785038). People believed they knew which opioid they were taking, and most of them were wrong. It is one small study in one city, but it is the clearest evidence yet that cychlorphine is replacing other opioids without the people using them knowing.

The potency is high and unpredictable. The 10-times-fentanyl estimate comes from in vitro (cell-based) receptor work shared by the Ghent University group as a personal communication and cited in CFSRE’s alert. It is not yet published, and receptor potency in a dish does not translate cleanly to a human dose. What is published is the closest relative: in a 2024 study of the orphine family, chlorphine was among the strongest activators of the mu-opioid receptor and caused some of the most pronounced breathing depression in mice (PMID 39154855). Those mice received 15 mg/kg by injection into the abdomen, a dose chosen to measure effects, not to model street use. Cychlorphine is chlorphine with an added chemical group, so this tells us the family is dangerous. It does not give us cychlorphine’s exact strength.

It usually comes with other depressants. Across CFSRE’s cases, cychlorphine appeared with fentanyl, methamphetamine, the designer benzos bromazolam and phenazolam, cocaine, nitazenes, and other orphines. UNODC added xylazine and medetomidine to that list. Benzos, xylazine and medetomidine all slow breathing or deepen sedation, and naloxone does not reverse any of them. Stacking an opioid with a sedative is how a survivable dose becomes a fatal one.

How it shuts down breathing

All opioids activate mu-opioid receptors in the brainstem areas that set your breathing rhythm. Activate enough of them and the brain stops responding to rising carbon dioxide, so breaths get slower and shallower until they stop. Oxygen falls, the heart slows, and without help, brain injury and death follow within minutes.

A very potent opioid shrinks the gap between a dose that feels like something and a dose that stops breathing. When that opioid is hidden inside a pill sold as Xanax, the person taking it has no tolerance and no reason to have naloxone nearby.

What naloxone can and cannot do

Naloxone pushes opioids off the mu receptor. The evidence that it works on cychlorphine is thin but consistent so far:

• Human evidence (case report, the weakest tier): the confirmed cychlorphine patient responded to 6 mg of intranasal naloxone, which is 1.5 standard 4 mg sprays (PMID 42481906).
• Animal evidence: in the 2024 mouse study, naloxone given before some orphines did not fully block breathing depression (PMID 39154855). That setup tests blocking, not rescue, and used a very high injected dose. It is a reason for caution, not proof that naloxone fails.
• The closest human comparison: nitazenes, another non-fentanyl class, have more data. In an Australian cohort of lab-confirmed nitazene poisonings, standard naloxone doses usually worked, but 45 percent of treated patients needed repeat doses (PMID 40810707). A 2026 review found no support for routinely using very high doses (PMID 42392847).

The practical reading: carry at least two doses, expect you may need both, and call emergency services even if the person wakes up. Naloxone can wear off before a long-acting opioid does, and if a benzo or xylazine is also involved, the person may keep breathing poorly after the opioid part is reversed.

How to protect yourself

1. Assume any pill not from a pharmacy could contain it. Fake Xanax, Percocet and OxyContin are the main routes into people without opioid tolerance. A pill that looks perfect tells you nothing; pill presses are cheap.

2. Know what your tests can and cannot see. A 2023 lab study ran two major fentanyl strip brands against 251 synthetic opioids. Neither detected brorphine or any of the 31 non-fentanyl opioids tested (PMID 38057832). Cychlorphine was not in that panel, but it shares brorphine’s backbone, so there is no reason to expect a strip to catch it. Industry references also list it as undetected by nitazene strips. Keep using fentanyl test strips, because fentanyl is still far more common, but read a negative as “no fentanyl detected,” never as “no opioid.” Reagent kits identify your intended drug and flag substitutions; see our test kit guide. Only lab mass spectrometry identifies cychlorphine itself, and our drug checking services list covers where that is still available.

3. Never use alone. This matters more than any test. If you are by yourself, the Never Use Alone hotline (1-800-484-3731) stays on the phone and sends help to your location if you stop responding.

4. Carry naloxone, and make sure the people around you know where it is. It is sold over the counter at US pharmacies, and NEXT Distro mails it free to most states.

5. Start with a fraction and wait. With an unknown pill or powder, take a small amount and wait well past the usual onset before taking more. Ingested pills can take an hour to peak.

6. Do not stack depressants. Alcohol, benzos, GHB and other opioids all multiply opioid breathing depression. Check combinations in our interaction checker.

What an overdose looks like, and what to do

Signs: will not wake to a firm knuckle rub on the breastbone, breathing slower than one breath every 5 seconds or stopped, gurgling or snoring sounds, blue or gray lips and fingertips, pinpoint pupils.

1. Call 911. Most states have Good Samaritan laws that protect people who call for help.
2. Give naloxone. One spray in one nostril.
3. Breathe for them if you know rescue breathing: head tilted back, one breath every 5 seconds.
4. Second dose after 2 to 3 minutes if they are not breathing on their own, in the other nostril.
5. Recovery position once they are breathing: on their side, top knee bent forward.
6. Stay with them. Overdose can return as naloxone wears off.

The bottom line

Cychlorphine is an opioid that fentanyl test strips cannot see, most often hidden in fake benzo and painkiller pills, and at least as dangerous as fentanyl. Naloxone still works, so carry two doses, never use alone, and treat every unverified pill as a possible opioid. If you also use stimulants, our cocaine guide and MDMA guide cover the testing that catches what can be caught.

Sources

PMID 42481906 | PMID 42785038 | PMID 39154855 | PMID 38057832 | PMID 40810707 | PMID 42392847 | PMID 41507112 | CFSRE Public Alert, January 2026 | UNODC Early Warning Advisory, May 2026