Emerging Synthetic Opioids: What to Know About Orphines in the Illicit Drug Supply

Rising reports from public health and law enforcement agencies showcase the appearance of a novel class of synthetic opioids, known as “orphines,” in the United States illicit drug supply. These new agents are described as highly potent μ-opioid receptor agonists that can cause significant risk for fatal respiratory depression.

The rise of these compounds displays the current evolving challenges within the ongoing opioid use disorder (OUD) crisis and brings attention to the need for health care specialists to be aware and prepared to recognize, manage, and mitigate overdose risk associated with increasingly potent and unpredictable synthetic opioids.¹^,²

What Are Orphines, and How Do They Work?

In the 1960s, orphines—a class of synthetic opioids—were synthesized with the intention of developing potent analgesics, similarly to how fentanyl was developed. Ultimately, these synthetic opioids were abandoned due to the severe safety concerns that follow, such as profound respiratory depression and high abuse potential.³

From a pharmacological standpoint, orphines behave as strong agonists at the μ-opioid receptor, similar to fentanyl but with significantly greater potency. Preliminary toxicological analyses indicate that some analogues may exceed fentanyl potency multiple-fold, increasing the likelihood of rapid-onset overdose.¹ These analyses align with broader trends observed with emerging synthetic opioids such as nitazenes, which have been tied to increased overdose mortality due to their potency and unpredictability.⁴

The primary concern remains in the fact that many of these compounds may not be detected by standard toxicology screens, which can lead to complications in diagnosis and surveillance efforts.¹ This limitation may cause underreporting of overdose cases.

Appearance in the Illicit Drug Supply

The emergence of orphines appears to follow regulatory actions targeting fentanyl analogues. The Drug Enforcement Administration implemented classwide scheduling of fentanyl-related substances in 2018, prompting illicit manufacturers to utilize alternative compounds.²

Orphine analogues are being identified in counterfeit pills and adulterated drug supplies such as stimulants like methamphetamine, according to recent forensic and toxicology reports.¹ Similarly to previous waves of synthetic opioid emergence, these substances may be introduced to enhance potency or reduce production costs, increasing the risk of unintentional exposure among users.⁴

The rapid evolution of synthetic opioids designed to evade legal controls is documented by international monitoring agencies, including the United Nations Office on Drugs and Crime, further indicating the likelihood of continuous spreading.⁵

Overdose Recognition and Clinical Management

In a clinical context, being exposed to highly potent synthetic opioids such as orphines may result in adverse effects, including rapid-onset respiratory depression, decreased level of consciousness, and death. Although these are present and consistent with other high-potency opioids, the effects may occur more quickly and with smaller quantities.¹

It is of note that reversal with naloxone continues to prove effective; however, higher or repeated dosing may be required due to the potency and receptor binding characteristics of these agents.⁶ This is congruent with clinical data on fentanyl and its analogues, where multiple naloxone administrations are often necessary.

Due to the inability of standard toxicology screens to detect these substances, new challenges emerge for emergency response and postmortem analysis, highlighting the importance of clinical suspicion in unexplained overdoses.

References

1. Armenian P, Vo KT, Barr-Walker J, Lynch KL. Fentanyl, fentanyl analogs and novel synthetic opioids: A comprehensive review. Neuropharmacology. 2018;134(Pt A):121-132. doi:10.1016/j.neuropharm.2017.10.016

2. Drug Enforcement Administration. Schedules of controlled substances: temporary placement of fentanyl-related substances in Schedule I. 21 CFR Part 1308. Fed Regist. February 6, 2018. Accessed May 5, 2026. https://www.federalregister.gov/documents/2018/02/06/2018-02319/schedules-of-controlled-substances-temporary-placement-of-fentanyl-related-substances-in-schedule-i

3. Vardanyan RS, Hruby VJ. Fentanyl-related compounds and derivatives: current status and future prospects for pharmaceutical applications. Future Med Chem. 2014;6(4):385-412. doi:10.4155/fmc.13.215

4. Kariisa M, Patel P, Smith H, Bitting J. Notes from the Field: xylazine detection and involvement in drug overdose deaths - United States, 2019. MMWR Morb Mortal Wkly Rep. 2021;70(37):1300-1302. doi:10.15585/mmwr.mm7037a4

5. United Nations Office on Drugs and Crime. Synthetic opioids in global drug markets. 2023. Accessed May 5, 2026.

6. Kim HK, Nelson LS. Reversal of opioid-induced ventilatory depression using low-dose naloxone (0.04 mg): a case series. J Med Toxicol. 2016;12(1):107-110. doi:10.1007/s13181-015-0499-3