Tox In Focus

Focused Clinical Reference

Vol. 21 · Heroin · July 2026

Drug Quick Reference

Drug Class / Mechanism

Semi-synthetic opioid (diacetylmorphine)

Schedule I

Street Names

Dope, smack; black tar heroin

'China White' (often fentanyl)

Routes of Administration

Injection, insufflation, smoked

Often adulterated with fentanyl

Commonly Detected With

Fentanyl (common adulterant), xylazine · Codeine contaminant, quinine, levamisole

Metabolism

Heroin to 6-MAM to morphine

Codeine also converts to morphine (CYP2D6)

Window of Detection

Urine 6-MAM: up to ~24 h

Urine morphine/codeine: ~1 to 2 days

Control Status

DEA Schedule I

HEROIN

6-MAM confirms heroin, and telling it apart from poppy seed and prescription opioids

Heroin (diacetylmorphine) is a Schedule I opioid that rapidly metabolizes to 6-monoacetylmorphine (6-MAM) and then morphine. Detecting 6-MAM is the specific marker of heroin use, but its short window means remote use may show only morphine, which overlaps with poppy seed and prescription opioids.¹

Why This Matters Now

Illicit heroin is now frequently adulterated with fentanyl and fentanyl analogues, and increasingly xylazine, which raise overdose risk and are not detected by an opiate screen or by heroin-marker testing.² A heroin-positive result should prompt consideration of these co-present adulterants.

⚠ Morphine and codeine positives are not specific to heroin; poppy seeds and prescribed opioids can produce them. Only 6-MAM confirms heroin, and its short window means its absence does not exclude heroin use.³

Clinical Presentation

INTOXICATION

Euphoria then sedation

Miosis

Respiratory depression

Analgesia

Overdose: CNS and respiratory depression, death

WITHDRAWAL

Onset within hours of last use

Anxiety, agitation

Myalgia, GI upset

Rhinorrhea, lacrimation, yawning

Craving

Important: Illicit heroin commonly contains fentanyl and may contain xylazine; xylazine is not reversed by naloxone. A heroin-positive sample warrants attention to these adulterants.

UDT Considerations

LC-MS/MS measures 6-MAM, morphine, and codeine. 6-MAM with morphine (with or without codeine) indicates heroin use; because 6-MAM clears within about a day, remote heroin use may show only morphine, or morphine and codeine.³ Poppy seed ingestion and legitimate morphine or codeine use can also produce morphine and codeine positives, so interpret the pattern carefully.⁴

Clinical Guidance

Treat 6-MAM as the specific confirmation of heroin use.³
Do not exclude heroin on a 6-MAM negative; its window is short (~24 h).³
Distinguish poppy seed and prescription opioids when only morphine or codeine is present.⁴
Test for fentanyl and xylazine separately; heroin markers do not detect them.
Use the analyte-pattern grid to guide interpretation.

Point-of-Care Testing Availability

Available strips

Opiate immunoassays detect morphine and codeine but not 6-MAM specifically.

Clinical use

They do not detect fentanyl, a common heroin adulterant.

Limitations

LC-MS/MS measures 6-MAM, morphine, and codeine to confirm heroin.

HEROIN | Clinical & Program Guidance

Tox In Focus Vol. 21 · July 2026 · Page 2 of 2

Interpreting the Test Result

▲ If Testing Is Positive

6-MAM confirms heroin. Its presence is specific; its short window means absence does not exclude heroin.³

Morphine/codeine are not specific. Poppy seed and prescription opioids can cause them; use the pattern grid.⁴

Consider adulterants. Fentanyl and xylazine often accompany heroin and need separate testing.

▼ If Testing Is Negative or Not Done

Does not exclude recent heroin. 6-MAM clears fast; a negative panel can still follow heroin use.

Timing and cutoff. Absence may reflect timing of last use or levels below the cutoff.

Adulterants not covered. A negative heroin panel says nothing about fentanyl or xylazine.

Analyte Pattern Interpretation

6-MAM	Morphine	Codeine	Interpretation
Pos	Pos	+/-	Heroin use confirmed.
Pos	Neg	Neg	Consistent with heroin; interpret with caution.
Neg	Pos	Pos	Not confirmed; heroin, poppy seed, or codeine use.
Neg	Pos	Neg	Morphine source: remote heroin, morphine, or poppy seed.
Neg	Neg	Pos	Codeine: prescription codeine or heroin contaminant.

6-MAM is the specific heroin marker but clears within ~24 h; morphine or codeine alone are not specific to heroin (poppy seed, prescription opioids).

Key References

Knight J, et al. Prevalence of heroin markers in urine for pain management patients. Forensic Sci Int. 2014;243:79-83.
Centers for Disease Control and Prevention. Increases in fentanyl drug confiscations and fentanyl-related overdose fatalities. 2015.
White RM, Black ML. Pain Management Testing Reference. AACC Press; 2007.
Concheiro M, et al. Morphine and codeine in oral fluid after controlled poppy seed administration. Drug Test Anal. 2015;7(7):586-591.

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