Tox In Focus

Focused Clinical Reference

Vol. 03 · Carfentanil · May 2026

Drug Quick Reference

Drug Class / Mechanism

Synthetic opioid; fentanyl analogue

~100x fentanyl; 10,000x morphine

Street Names

'C-50', 'Gray death'

Often unlabeled in counterfeit pills

Routes of Administration

Oral (counterfeit tablets)

Intravenous injection

Commonly Detected With

Fentanyl, cychlorphine · Nitazenes, xylazine

Metabolism

Hepatic CYP3A4

Active metabolite: norcarfentanil

Window of Detection

Urine ~2 to 4 days (estimated)

IA panels unreliable

Control Status

DEA Schedule II

CARFENTANIL

A large-animal tranquilizer now driving mass-casualty opioid overdoses

Carfentanil is a fentanyl analogue originally developed to tranquilize large animals such as elephants and rhinos. At an estimated 100 times the potency of fentanyl and 10,000 times morphine, a dose invisible to the naked eye can be lethal in humans. It has no approved human medical use and is now detected across 37 US states in counterfeit pills and the illicit opioid supply.¹

Why This Matters Now

DEA labs confirmed more than 100 kg of carfentanil-containing seizures in 2024, exceeding the prior three years combined, and overdose deaths involving carfentanil rose sevenfold in a year (29 in January to June 2023 to 238 in January to June 2024). A single 2025 DEA operation in LA County yielded 628,000 counterfeit carfentanil tablets.¹

⚠ Carfentanil now appears in counterfeit M30 oxycodone and hydromorphone tablets that are indistinguishable from legitimate pills. Standard naloxone doses are frequently insufficient; assume potential carfentanil exposure in any patient using illicit opioids.

Clinical Presentation

INTOXICATION

Rapid loss of consciousness

Pinpoint pupils (miosis)

Profound respiratory depression

Apnea; respiratory arrest

Bradycardia, hypotension

Cyanosis

WITHDRAWAL

Rapid onset after naloxone

Severe anxiety / agitation

Diaphoresis

Nausea / vomiting

Tachycardia, hypertension

Muscle cramping / pain

Important: Standard naloxone doses (0.4 to 2 mg) are frequently insufficient. Use 4 mg IM/IV as the initial dose and repeat every 2 to 3 minutes; cumulative doses of 10 to 12 mg or more have been required. Anticipate resedation and maintain continuous monitoring for at least 4 to 6 hours after apparent reversal.

UDT Considerations

Carfentanil is not detected by standard opioid immunoassay panels, and fentanyl test strips and fentanyl IA antibodies do not reliably cross-react with it at clinically relevant concentrations. Confirmatory identification requires LC-MS/MS with a panel that specifically includes carfentanil and its active metabolite norcarfentanil; confirm coverage with your laboratory.¹ A negative IA or point-of-care test does not rule out carfentanil; treat based on presentation.³

Clinical Guidance

Administer naloxone immediately and aggressively; 4 mg IV/IM is an appropriate starting dose, repeated every 2 to 3 minutes and titrated to respiratory response, with 4 to 6 hours of monitoring for resedation.²
Treat any counterfeit pill or unknown powder as potential carfentanil; standard UDT will not detect it.
Order LC-MS/MS with explicit carfentanil and norcarfentanil coverage.¹
Report confirmed cases to DEA and your state health department for surveillance.¹
Maintain high suspicion in any illicit-opioid exposure; presentation drives care.

Point-of-Care Testing Availability

Available strips

Standard fentanyl test strips do not reliably detect carfentanil.

Clinical use

Point-of-care IA panels will not flag it at clinically relevant concentrations.

Limitations

LC-MS/MS with carfentanil and norcarfentanil coverage is required.

CARFENTANIL | Clinical & Program Guidance

Tox In Focus Vol. 03 · May 2026 · Page 2 of 2

Interpreting the Test Result

▲ If Testing Is Positive

Confirms carfentanil exposure. LC-MS/MS with carfentanil/norcarfentanil coverage; standard IA and strips miss it.

Any amount is an emergency. Given ~100x fentanyl potency, any detectable amount is clinically critical.

Expect naloxone resistance. Standard doses are often insufficient; use high, repeated dosing and monitor for resedation.

▼ If Testing Is Negative or Not Done

Screen and strips prove nothing. Fentanyl immunoassay and test strips do not reliably detect carfentanil.

Confirm panel coverage. Ensure the LC-MS/MS panel explicitly includes carfentanil and norcarfentanil.

Treat clinically. A negative does not rule out exposure; presentation guides care.

Metabolism & Urinary Markers

Carfentanil analytes measured on definitive testing.

Metabolite	Clinical Significance
Carfentanil (parent)	Fentanyl analogue; ~100x fentanyl; the primary LC-MS/MS target.
Norcarfentanil	Active metabolite; include it in the confirmatory panel.

Key References

US Drug Enforcement Administration. Intelligence report on carfentanil. 2025.
HMP Global EMS World. Carfentanil and EMS response. 2025.
Centers for Disease Control and Prevention, National Center for Health Statistics. Drug overdose data brief. 2024.

DISCLAIMER: This document is intended for clinical reference and educational purposes only. It does not constitute medical, legal, or professional advice and should not replace independent clinical or programmatic judgment. Content reflects published data available at time of preparation. ToxiPharm LLC makes no warranties regarding completeness or applicability in all settings. | © 2026 ToxiPharm LLC | toxipharm.org