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Clinical Toxicology Intelligence

Issue

#03

May 2026

The New Synthetic Opioid Fentanyl Strips Cannot Find

The DEA's May 12 public safety advisory confirmed 78 postmortem cases in the United States and United Kingdom, including 41 overdose deaths in Knox County, Tennessee alone. Cychlorphine is estimated to be approximately 10 times more potent than fentanyl. It is appearing in street supply samples and postmortem toxicology with increasing frequency, and it carries two properties that make it distinctly dangerous: it is not detected by standard fentanyl immunoassay test strips, and it may require multiple naloxone doses for reversal.

The advisory flags fentanyl as now being routinely mixed with cychlorphine, medetomidine, xylazine, and nitazenes. That combination matters clinically: medetomidine and xylazine are alpha-2 agonists whose sedation is not reversed by naloxone. A single overdose presentation can involve agents requiring both aggressive naloxone dosing and sustained supportive care that naloxone cannot provide.

Source: DEA Public Safety Advisory  ·  May 12, 2026

In effect: December 3, 2024

Your BZO Panel Has a Blind Spot: Designer Benzodiazepines and the Scheduling Gap

Bromazolam was placed under international scheduling controls on December 3, 2024. By November 2024, drug checking surveillance in Canada, the United Kingdom, Australia, and Germany was already showing bromazolam declining and a direct structural replacement, ethylbromazolam, appearing in its place. The substitution was essentially instantaneous.

Ethylbromazolam (also called bromoethylazolam) is a triazolo-benzodiazepine with comparable GABA-A receptor potency to bromazolam. It is not detected on standard BZO immunoassays, which are calibrated to classical benzodiazepines via oxazepam equivalents. The DEA has not yet scheduled it in the United States. Published this month in Archives of Toxicology, a full pharmacological and emergence characterization confirms both its potency and the global substitution pattern. Additional designer benzodiazepines are appearing alongside it: desalkylgidazepam and clobromazolam are both showing up in international drug checking data.

A patient presenting with clinical BZO-like sedation and a negative standard BZO immunoassay screen may be using ethylbromazolam or a related designer triazolo-benzodiazepine. Detection requires LC-MS/MS with these specific compounds included in the panel. For drug courts and OTPs ordering BZO panels: a negative result no longer rules out this class. If you consult on laboratory panel design, ask whether the confirmation method covers triazolam-class designer BZDs. Most current clinical confirmation menus do not.

Norman C, et al. Global emergence and GABA-A receptor activity of ethylbromazolam. Arch Toxicol. 2026. doi:10.1007/s00204-026-04433-9  ·  PMID 42159737

J ADDICT MED

"Prolonged Fentanyl Detection on UDT: A Case for Revising Interpretation Frameworks in Chronic Use"

Two patients with chronic OUD remained intermittently fentanyl-positive for 170 days and 210 days, respectively, after self-reported last use. Both were tested at a 0.5 ng/mL cutoff (UCSF). In both cases, the prolonged positive results directly delayed child custody reunification. The standard framework for fentanyl detection cites 1 to 3 days, a figure derived from studies at higher cutoffs in acute use settings. At 0.5 ng/mL in a chronic heavy user, the mechanism is different: extensive lipophilic tissue accumulation with slow redistribution back into urine. Low-level intermittent positivity is not the same pharmacokinetic profile as a recent use event, but current interpretation guidance does not distinguish between the two. This is a two-case report with self-reported last use dates. The evidence level is limited. The mechanism is sound, and the custody consequences were real.

Plaza N, Hernandez T, Vais S. J Addict Med. Published online May 11, 2026. doi:10.1097/ADM.0000000000001707  ·  PubMed →

J ANAL TOXICOL

"False Positive Urine Drug Screens: A Systematic Review (2013–2024)"

Saitman and colleagues reviewed 61 studies drawn from 569 publications covering cross-reactivity and false positive interferences in immunoassay-based urine drug screens across opioids, amphetamines, benzodiazepines, cannabinoids, barbiturates, PCP, cocaine, ethanol, and EtG. The review updates and supersedes the 2013-era literature that still underpins most clinical guidance on UDT false positives. It classifies evidence by level, from single case reports through controlled spiking experiments, and emphasizes the ongoing need for laboratorian-clinician communication and confirmatory testing for all presumptive positives.

Saitman A, Fitzgerald RL, Lund K, Suhandynata RT, Menlyadiev M. J Anal Toxicol. 2026;50(4). doi:10.1093/jat/bkag007  ·  PMID 41639014