Brorphine: Complete Toxicology, Overdose, Dependence, Withdrawal & Safety Monograph
What the evidence actually shows
Evidence Moderate: strong receptor/forensic evidence, multiple fatal and nonfatal human intoxications, limited direct dependence/withdrawal researchDirect answer
Reference-grade brorphine monograph covering history, orphine chemistry, mu-opioid pharmacology, fatal and nonfatal intoxications, fentanyl/benzodiazepine co-exposure, respiratory depression, naloxone, dependence and withdrawal, treatment support, metabolism, toxicology testing, forensic interpretation, legal status, and the newer orphine wave. Brorphine is a potent benzimidazolone synthetic opioid and the first major drug-market member of the family now commonly called the orphines. It emerged in the illicit market in 2019 and became prominent in U.S. forensic casework in 2020 as isotonitazene detections declined. A 20-case forensic series found fentanyl in 100% of brorphine-positive cases and flualprazolam in 80%, showing that the early U.S. signal was deeply embedded in a high-risk polysubstance supply.
Research brief
Questions this page answers
- What is brorphine?
- Is brorphine an orphine opioid?
- How is brorphine related to fentanyl or nitazenes?
- Can brorphine cause fatal overdose?
- Does naloxone work for brorphine overdose?
- Can brorphine cause dependence and withdrawal?
- Why was brorphine often found with fentanyl and flualprazolam?
- How is brorphine metabolized and detected?
- Can routine opioid testing miss brorphine?
- What is the legal status of brorphine?
- How did brorphine lead into the newer orphine market?
Signal
Scientific takeaways
- Brorphine is a potent benzimidazolone synthetic opioid and the first major drug-market member of the family now commonly called the orphines.
- It emerged in the illicit market in 2019 and became prominent in U.S. forensic casework in 2020 as isotonitazene detections declined.
- A 20-case forensic series found fentanyl in 100% of brorphine-positive cases and flualprazolam in 80%, showing that the early U.S. signal was deeply embedded in a high-risk polysubstance supply.
- DEA reported at least 21 U.S. fatalities associated with brorphine between August 2019 and June 2021; published case reports and the 2026 review document both fatal and nonfatal intoxications.
- Brorphine is a potent mu-opioid receptor agonist; preclinical studies demonstrate opioid-like antinociception, respiratory depression, and abuse potential. These findings do not establish a safe human dose.
- Human metabolism studies identify numerous brorphine metabolites, with N-oxidation prominent in authentic urine; LC-MS/MS and LC-HRMS are central to definitive detection.
- Physical dependence and opioid withdrawal are biologically expected with repeated potent MOR agonism, but a brorphine-specific prospective withdrawal timeline or validated taper has not been established.
- Brorphine became permanently U.S. Schedule I effective April 5, 2023 and is internationally controlled in Schedule I of the 1961 Single Convention following the 2022 CND decision.
Brorphine: Complete Toxicology, Overdose, Dependence, Withdrawal & Safety Monograph
Emergency safety: Brorphine is a potent opioid. If someone is difficult or impossible to wake, breathing slowly or irregularly, blue/gray around the lips, choking/gurgling while unresponsive, or has collapsed after an unknown opioid product, call emergency services and administer naloxone if available.
Quick answer
Brorphine is a potent synthetic opioid and the first major illicit-market member of the benzimidazolone family now commonly called the “orphines.”
It is chemically distinct from fentanyl and from the nitazenes, but it converges on the same dangerous pharmacology: strong mu-opioid receptor (MOR) agonism capable of producing profound sedation and respiratory depression.
Brorphine became visible in the NPS market in 2019. In the United States, it rose sharply during 2020 as isotonitazene detections declined. The strongest early U.S. case series found brorphine in 20 authentic forensic cases; fentanyl was present in all 20 and flualprazolam in 80%. PMID 33201526
That finding makes brorphine an especially important example of polysubstance opioid/benzodiazepine risk, not simply a molecule with an alarming receptor potency.
By 2026, brorphine had become historically important for a second reason: newer chlorinated, fluorinated, iodinated and cyclized analogues had begun emerging as the broader orphine family. PMID 41622550
Evidence at a glance
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| Question | Best current evidence |
|---|---|
| Is brorphine an opioid? | Yes. Potent MOR agonist. |
| Chemical family | Benzimidazolone / orphine-family opioid. |
| Approved medical use? | None. |
| Human fatality evidence? | Yes. Multiple fatal cases and national regulatory case counts. |
| Human nonfatal toxicity? | Yes. Published cases include serious systemic complications. |
| Respiratory depression evidence | Strong preclinical evidence plus opioid-class human toxidrome/fatalities. |
| Naloxone relevant? | Yes. |
| Physical dependence possible? | Strongly expected from potent MOR agonism; direct brorphine-specific longitudinal data are sparse. |
| Routine screening reliable? | No guarantee. Targeted LC-MS methods are important. |
| Safe recreational dose? | Not established. |
| U.S. status | Permanent Schedule I effective April 5, 2023; temporarily Schedule I since March 1, 2021. |
| International status | Schedule I of the 1961 Single Convention since 2022. |
Identity
Canonical name: Brorphine
CAS: 2244737-98-0
Molecular formula: C20H22BrN3O
Class: benzimidazolone / orphine synthetic opioid
Primary target: mu-opioid receptor
Approved medical use: none
UNODC classifies brorphine in the orphine analogue group.
This is important because brorphine was once commonly discussed simply as a “novel synthetic opioid.” In retrospect, it was the first high-profile member of a structural family that has since produced:
- orphine;
- fluorphine;
- chlorphine;
- iodorphine;
- cychlorphine;
- spirochlorphine;
- spirobrorphine;
- other halogenated/cyclized analogues.
History: why brorphine appeared when it did
Brorphine emerged in drug markets around 2019.
Its rise was closely linked to changes in the novel-opioid market.
Isotonitazene had become a leading NPS opioid in the United States during 2019–2020. After DEA announced scheduling action against isotonitazene, forensic investigators observed a decline in isotonitazene and a rise in brorphine. PMID 33201526
That is a recurring feature of NPS markets:
- one potent opioid becomes prevalent;
- surveillance and control catch up;
- a structurally different substitute appears.
Brorphine was therefore both an opioid threat and an early warning about chemical market substitution.
Early public-health alert
CFSRE issued a U.S. public-health alert in July 2020 after brorphine was confirmed in seven blood specimens associated with fatalities across Minnesota, Illinois and Arizona. CFSRE
The alert emphasized:
- very high opioid potency;
- respiratory-depression risk;
- emergence outside fentanyl's chemical family;
- need for naloxone availability;
- need for laboratories to expand testing.
The 20-case U.S. forensic series
A 2021 study expanded the early signal to 20 authentic forensic cases.
The cases showed an extraordinary degree of polysubstance exposure:
- fentanyl: 100%
- flualprazolam: 80%
Mean brorphine blood concentration was 2.5 ± 3.1 ng/mL, with a median of 1.1 ng/mL and range of 0.1–10 ng/mL. PMID 33201526
What that finding means
It demonstrates that brorphine was embedded in an already dangerous opioid/benzodiazepine supply.
What it does NOT mean
It does not prove:
- brorphine alone caused every death;
- 0.1 or 10 ng/mL is a universal toxic threshold;
- every brorphine product contains fentanyl;
- flualprazolam is chemically part of brorphine.
The correct interpretation is polysubstance market risk.
Federal fatality data
DEA's permanent scheduling order reported that brorphine had been associated with at least 21 U.S. fatalities between August 2019 and June 2021.
DEA also reported:
- illicit-market detections across multiple countries beginning in 2019;
- 157 NFLIS-Drug reports from April 2020 through June 2022;
- no accepted medical use in the United States. Federal Register
Again, “associated with” is not identical to “sole cause.”
Direct fatal case report
A 2021 clinical-toxicology report documented a death associated with brorphine. PMID 33522844
Single cases cannot establish population risk, but they add direct clinical context to the larger forensic signal.
Nonfatal severe toxicity
A separate case report described severe rhabdomyolysis and acute kidney failure after brorphine exposure in a patient receiving chronic sertraline therapy. PMID 34052902
The case does not establish a general brorphine–sertraline interaction rule.
It shows that severe brorphine intoxication can involve complications beyond simple sedation.
Pharmacodynamics
Mu-opioid receptor agonism
Brorphine is a potent MOR agonist.
MOR activation can produce:
- analgesia;
- euphoria;
- sedation;
- miosis;
- respiratory depression;
- gastrointestinal slowing;
- tolerance;
- physical dependence.
A 2021 pharmacology/metabolism study also found brorphine to be a weak partial kappa-opioid receptor agonist in the assay used. PMID 34509061
The clinical importance of the KOR component is uncertain.
Respiratory depression: direct preclinical evidence
A 2024 comparative study tested brorphine and several related orphine analogues.
The compounds bound MOR with nanomolar affinity, and brorphine was among the strongest functional MOR agonists.
In mice, brorphine produced:
- strong antinociception;
- substantial respiratory-depressant effects. PMID 39154855
Those animal findings strengthen the mechanistic basis for human respiratory-overdose concern.
They do not establish a human safe dose or a human potency ratio.
Is brorphine “as strong as fentanyl”?
Early alerts and experimental literature have described brorphine potency as similar to or somewhat below fentanyl depending on assay.
WHO summarized it as more potent than morphine and less potent than fentanyl in the evidence it reviewed during international scheduling.
None of those statements creates a human milligram conversion.
The correct lesson is:
Brorphine has enough MOR activity to cause severe opioid toxicity at low concentrations, and illicit products do not provide a reliable margin for error.
Naloxone
Because brorphine is a MOR agonist, naloxone is appropriate for suspected brorphine overdose.
CFSRE's original alert specifically recommended making naloxone available in response to brorphine's emergence.
No special brorphine bystander dose
There is no validated brorphine-specific consumer naloxone regimen.
In an emergency:
- call emergency services;
- administer available naloxone according to product/emergency instructions;
- support breathing if trained;
- repeat naloxone if indicated by emergency guidance;
- remain with the person.
The fact that brorphine often appears with fentanyl and benzodiazepines makes ongoing monitoring particularly important.
Fentanyl + brorphine
Every case in the early 20-case U.S. series included fentanyl.
Two potent MOR agonists can increase:
- respiratory depression;
- sedation;
- hypoxia;
- risk of death.
A user may not know brorphine is present at all.
This is why an “opioid dose” cannot be understood from one drug name when the product itself may contain multiple opioids.
Designer benzodiazepines + brorphine
Flualprazolam was present in 80% of the 20 early brorphine cases.
Benzodiazepine-type drugs can:
- deepen sedation;
- impair airway-protective responses;
- reduce the ability to respond as opioid respiratory depression worsens.
Naloxone can reverse the opioid component.
It does not reverse benzodiazepine sedation.
Metabolism
A detailed 2021 study used:
- pooled human liver microsomes;
- authentic forensic blood/urine;
- LC-HR-MS/MS.
Researchers identified:
- 14 metabolites in urine;
- 4 metabolites in blood.
The most prominent in-vivo urinary pathway involved N-oxidation, while in-vitro microsome work produced a somewhat different dominant metabolite pattern. PMID 34509061
This difference is a reminder that microsome studies do not perfectly reproduce living human metabolism.
Drug testing and biomonitoring
Published brorphine methods use:
- LC-MS/MS;
- LC-HRMS;
- high-resolution screening libraries;
- metabolite-aware analysis.
The 20-case study developed quantitative LC-MS/MS confirmation specifically because brorphine was outside many standard toxicology scopes. PMID 33201526
Routine immunoassays
There is not enough evidence to assume a standard hospital opioid immunoassay will reliably identify brorphine.
A negative routine opioid screen therefore should not override a classic opioid toxidrome when a novel synthetic opioid is possible.
Why metabolites matter
If the parent drug is:
- present at low concentration;
- already metabolized;
- outside the lab's targeted panel,
metabolite detection can improve confidence that exposure occurred.
The 2026 review notes that biomonitoring remains challenging, particularly as newer orphine analogues appear faster than certified standards and validated workflows. PMID 41622550
Tolerance
Repeated strong MOR agonism is expected to produce opioid tolerance.
Direct prospective brorphine tolerance studies are not available.
Tolerance can:
- make previous exposure feel weaker;
- encourage escalation;
- contribute to physical dependence.
Tolerance to subjective effects does not guarantee protection against respiratory depression—especially when product composition changes.
Physical dependence
WHO concluded brorphine had dependence potential similar to other opioids based on its pharmacology and available evidence.
Direct brorphine-specific longitudinal dependence cohorts are limited.
The evidence therefore supports:
- high biological plausibility;
- opioid-class concern;
- uncertainty about exact time-to-dependence in humans.
Withdrawal
No controlled brorphine-specific withdrawal timeline is established.
Expected opioid withdrawal may include:
- restlessness;
- anxiety;
- insomnia;
- sweating/chills;
- yawning;
- tearing/runny nose;
- muscle aches;
- abdominal cramping;
- nausea/vomiting;
- diarrhea;
- craving.
No validated brorphine self-taper
A product obtained from an illicit market may have:
- uncertain concentration;
- other opioids;
- benzodiazepines;
- changing formulation.
That makes a label-based home taper especially unreliable.
Dependence vs opioid use disorder
Physical dependence is a physiologic adaptation.
Opioid use disorder is a broader pattern that can include:
- inability to reduce use;
- craving;
- continued use despite harm;
- hazardous use;
- work/family problems;
- excessive time obtaining/using/recovering;
- tolerance;
- withdrawal.
They overlap but are not identical.
Treatment and support
There is no medication approved specifically for brorphine dependence.
Evidence-based opioid use disorder treatment applies.
Established medications include:
- buprenorphine;
- methadone;
- extended-release naltrexone in appropriately selected patients.
This article does not provide home induction doses or a DIY withdrawal schedule.
For U.S. treatment resources:
- FindTreatment.gov
- SAMHSA National Helpline: 1-800-662-HELP (4357)
Forensic interpretation
A brorphine-positive death does not automatically establish brorphine as the only cause.
Interpretation requires:
- complete toxicology;
- fentanyl and benzodiazepine findings;
- tolerance;
- medical history;
- scene evidence;
- concentration;
- specimen type;
- postmortem effects.
The early U.S. case series is a perfect example: brorphine was real, clinically relevant, and consistently found in deaths—but every one of those 20 cases also contained fentanyl.
From brorphine to the modern orphines
Brorphine's long-term importance became clearer in 2024–2026.
A 2024 laboratory study examined brorphine alongside:
- orphine;
- fluorphine;
- chlorphine;
- iodorphine.
All bound MOR with nanomolar affinity, and several produced strong opioid effects and respiratory depression in animals. PMID 39154855
By 2026, CFSRE was warning about a broader wave of benzimidazolone/orphine opioids, including:
- chlorphine;
- cychlorphine;
- spirochlorphine;
- spirobrorphine;
- 5,6-dichloro-brorphine;
- related analogues.
Brorphine was therefore not an isolated dead-end compound.
It was the first major warning from a family that later diversified.
See the Orphine opioids monograph.
Legal and regulatory history
United States
DEA temporarily placed brorphine into Schedule I effective March 1, 2021 because of an imminent hazard to public safety.
After international scheduling, DEA permanently placed brorphine into Schedule I effective April 5, 2023. Federal Register
The final order noted:
- at least 21 associated U.S. fatalities from August 2019–June 2021;
- no accepted medical use in the United States;
- 157 NFLIS reports from April 2020–June 2022.
International
WHO's 44th Expert Committee on Drug Dependence recommended international control.
In March 2022, the UN Commission on Narcotic Drugs voted to place brorphine in Schedule I of the 1961 Single Convention, and the decision entered into force after notification on May 27, 2022. UNODC
Special populations
There are no controlled brorphine studies establishing safety in:
- pregnancy;
- breastfeeding;
- children/adolescents;
- older adults;
- chronic lung disease;
- sleep apnea;
- liver disease;
- kidney disease.
Risk is especially concerning in:
- opioid-naive people;
- people taking fentanyl or other opioids;
- people using benzodiazepines/alcohol;
- people recently abstinent from opioids;
- people using alone.
The lack of data is not evidence of safety.
Myths and misconceptions
“Brorphine is a fentanyl analogue.”
No. It is a chemically distinct benzimidazolone/orphine opioid.
“Brorphine cases prove every sample contains fentanyl.”
No. The early U.S. forensic series had fentanyl in every case, but that describes those cases, not a chemical requirement.
“Flualprazolam is part of brorphine.”
No. It was a commonly co-detected designer benzodiazepine in the early market.
“A low blood concentration means the drug was weak.”
No. Brorphine can be clinically important at low ng/mL concentrations.
“Withdrawal is not proven, so dependence is unlikely.”
No. Potent MOR agonism and WHO's dependence assessment strongly support dependence risk; what remains uncertain is the exact brorphine-specific human timeline.
“Brorphine disappeared, so it is irrelevant.”
No. Its structural family has expanded into a new wave of orphine opioids.
What we know vs what remains unknown
Established
- brorphine is a potent MOR agonist;
- fatal and nonfatal human intoxications occur;
- early U.S. casework showed intense fentanyl/flualprazolam co-exposure;
- preclinical respiratory depression is documented;
- human metabolites are characterized;
- advanced LC-MS methods can identify it;
- U.S. and international Schedule I control is established.
Strongly plausible / class-supported
- tolerance;
- physical dependence;
- opioid withdrawal;
- loss-of-tolerance overdose risk;
- increased danger with other depressants.
Not established
- safe consumer dose;
- human fentanyl-equivalence ratio;
- universal toxic/lethal concentration;
- brorphine-specific withdrawal onset/peak/duration;
- validated home taper;
- controlled long-term human safety;
- pregnancy safety.
If brorphine exposure or dependence is suspected
Overdose now
Treat it as an opioid emergency:
- call emergency services;
- administer naloxone if available;
- support breathing if trained;
- remain with the person.
Dependence or loss of control
Medical/addiction assessment is appropriate if there is:
- withdrawal between uses;
- escalating use;
- repeated inability to stop;
- overdose;
- polysubstance opioid/benzodiazepine use;
- unknown product composition.
The exact opioid name is helpful, but treatment does not need to wait until every analogue is analytically identified.
Bottom line
Brorphine matters for two reasons.
First, it is a potent, lethal synthetic opioid with real human casework, heavy fentanyl/benzodiazepine co-exposure, documented respiratory-depressant pharmacology, and difficult toxicological detection.
Second, it turned out to be the opening chapter of the orphine family now re-emerging with compounds such as chlorphine, cychlorphine and spirochlorphine.
Its history captures the larger RC-opioid problem perfectly:
When one synthetic-opioid family is controlled, the market can migrate to another scaffold faster than routine testing, clinical familiarity, and public awareness can adapt.
Related evidence
Source ledger
References
14 sources
- 01Brorphine-Investigation and quantitation of a new potent synthetic opioid in forensic toxicology casework using liquid chromatography-mass spectrometry Krotulski AJ, Papsun DM, Noble C, Kacinko SL, Logan BK · 2021PMID 33201526DOI 10.1111/1556-4029.14623 PubMed →
- 02Pharmacological and metabolic characterization of the novel synthetic opioid brorphine and its detection in routine casework Grafinger KE, Wilde M, Otte L, Auwärter V · 2021PMID 34509061DOI 10.1016/j.forsciint.2021.110989 PubMed →
- 03First Report on Brorphine: The Next Opioid on the Deadly New Psychoactive Substance Horizon? Verougstraete N, Vandeputte MM, Lyphout C, et al. · 2021PMID 32744605DOI 10.1093/jat/bkaa094 PubMed →
- 04Death associated with brorphine, an emerging novel synthetic opioid Vohra V, King AM, Jacobs E, Aaron C · 2021PMID 33522844DOI 10.1080/15563650.2021.1879111 PubMed →
- 05Severe rhabdomyolysis and acute kidney failure due to synthetic opioid brorphine exposure in combination with chronic sertraline therapy Razinger G, Grenc D, Pezdir T, Kranvogl R, Brvar M · 2021PMID 34052902DOI 10.1007/s00228-021-03136-7 PubMed →
- 06Elucidating the harm potential of brorphine analogues as new synthetic opioids: Synthesis, in vitro, and in vivo characterization Vandeputte MM, Bilel S, Tirri M, et al. · 2024PMID 39154855DOI 10.1016/j.neuropharm.2024.110113 PubMed →
- 07Brorphine and Its Analogues: Pharmacology, Toxicology, and Biomonitoring Marchei E, Graziano S, Pichini S, Farré M · 2026PMID 41622550DOI 10.1097/FTD.0000000000001446 PubMed →
- 08Non-fentanyl-derived synthetic opioids emerging during recent years Review article · 2024PMID 37423031 PubMed →
- 09The Rise of Brorphine — A Potent New Synthetic Opioid Identified in the Midwestern United States Center for Forensic Science Research and Education · 2020 Source →
- 10Emerging Global Synthetic Opioid Threats: Benzimidazol-2-ones – The Orphines Center for Forensic Science Research and Education · 2026 Source →
- 11WHO Expert Committee on Drug Dependence: forty-fourth report World Health Organization · 2022 Source →
- 12CND decision on international control of brorphine and metonitazene enters into force United Nations Office on Drugs and Crime · 2022 Source →
- 13Schedules of Controlled Substances: Placement of Brorphine in Schedule I U.S. Drug Enforcement Administration · 2023 Source →
- 14Substance Use Disorder Treatment Substance Abuse and Mental Health Services Administration · 2026 Source →