Heroin & Street Opioids
Synthesis Route
Opium latex is processed: morphine is extracted, then acetylated with acetic anhydride to produce diacetylmorphine (heroin). The acetyl groups make the molecule fat-soluble — why heroin crosses the blood-brain barrier faster than morphine and produces a stronger rush.
Predictable Synthesis Byproducts
- 6-monoacetylmorphine (6-MAM) — incomplete acetylation; also heroin's primary active metabolite. Its presence in urine confirms heroin use specifically (not codeine or morphine).
- Acetylcodeine — from codeine in the original opium.
- Acetic acid / acetic anhydride traces — the "vinegar" smell of fresh heroin.
- Noscapine, papaverine, narcotine — non-opioid poppy alkaloids that survive extraction. Generally inert at typical exposures.
Typical Adulterants — Why This Category Is Different
For heroin, the probability estimate inverts. The question is not "is it cut" — it is "is there any heroin in it at all."
DEA 2024 data: fentanyl accounts for approximately 70% of all US overdose deaths (as a share of all overdose deaths — the CDC's opioid-specific figures give a slightly different denominator; see Module 4 for that framing). Fentanyl is the actual psychoactive in most "heroin" sold in many regions. The Philadelphia drug-checking program found 98% of samples sold as "heroin" contained fentanyl, median fentanyl content 5.8% by weight (range 0.1–64.9%) (Krotulski et al., 2025).
| Adulterant | Est. probability | Risk |
|---|---|---|
Fentanyl / fluorofentanyl |
Very high — ~70–98% depending on region | Wildly variable potency within a single bag → unpredictable overdose. ~2 mg can be fatal in opioid-naive users. (DEA, 2024; Krotulski et al., 2025) |
Xylazine"tranq" |
High in Northeast US — >50%; ~80% of opioid samples in parts of Maryland (CDC, 2024) | Severe sedation; naloxone-resistant respiratory depression; necrotic skin wounds at injection sites |
Medetomidineveterinary sedative |
Emerging — rising sharply 2024–2025; far more potent than xylazine (estimates vary widely by assay; figures in the range of ~100–200× have been reported in harm-reduction and forensic contexts) | Profound bradycardia, respiratory depression; naloxone-resistant |
BTMPSindustrial plastic stabilizer |
Emerging — newly detected 2024, prevalence climbing | Effects in humans largely unknown |
Local anestheticslidocaine, tetracaine |
Moderate | Mimic heroin numbness; cardiac risk in excess |
Quinine |
Low–moderate | Bitter taste matches heroin; generally inert at low doses |
Bulk fillerslactose, mannitol, starch |
Common | Generally inert |
Removal & Testing
Fentanyl cannot be removed from heroin. It is co-dissolved. Recrystallization does not separate them meaningfully.
- Fentanyl test strips — the single most important harm-reduction tool for any opioid. Dissolve a small sample in water, dip, read at 5 minutes.
- Xylazine test strips — now exist; recommended where xylazine prevalence is documented.
Naloxone does not reverse xylazine or medetomidine. Breathing can stay depressed after naloxone with these adulterants. Always call emergency services — do not assume naloxone is sufficient.
Practical floor: any US street opioid in 2025+ should be assumed to contain fentanyl unless tested otherwise. "I bought heroin" is no longer an accurate description of the product.
Sources: Full references for the citations in this submodule (Krotulski et al., 2025; DEA, 2024; CDC, 2024) are listed in the Module 10 Sources section.