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Heroin
diacetylmorphine
Heroin (diacetylmorphine) — smack, junk, dope — is a semi-synthetic opioid of the morphinan class. It is a prodrug of morphine, converted in the blood and brain to compounds with faster and more complete brain penetration.[1] It activates opioid receptors, suppressing pain signals and depressing the brainstem's drive to breathe.[2]
Heroin (diacetylmorphine) — smack, junk, dope — is a semi-synthetic opioid of the morphinan class. It is a prodrug of morphine whose lipophilicity enables rapid blood-brain barrier penetration.[1] Heroin acts as a full µ-opioid receptor agonist through its active metabolite 6-monoacetylmorphine,[2] suppressing pain signaling and depressing respiratory drive.
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C.R. Alder Wright first synthesized diacetylmorphine in 1874; Bayer commercialized it in 1898 as a non-addictive morphine substitute.[3] Addiction proved undeniable within a decade, and the 1961 UN Single Convention placed it in Schedule I.[4] In North American markets, illicitly manufactured fentanyl has largely displaced heroin since 2021.[5]
Subjective effects include profound pain suppression, euphoria, heavy sedation, anxiolysis, and a warm enveloping calm. The experience is defined by its onset — intravenous use produces a rapid, overwhelming wave of warmth that erases pain and distress, distinguishing it from the slower build of morphine. Nausea, severe constipation, pronounced itching, and slowed breathing are characteristic unwanted effects.
Heroin produces rapid physical dependence and has the narrowest safety margin of any commonly used substance.[6] Tolerance to euphoria develops faster than tolerance to respiratory depression,[7] so dose escalation closes the gap between intoxication and fatal overdose; mortality among untreated dependent people reaches 36.1 per 1000 person-years.[8] A century of clinical and forensic evidence underpins current understanding, though no controlled human dose-finding studies exist.
History[edit]
Discovery
Diacetylmorphine was first synthesized in 1874 by C.R. Alder Wright in London.[3] Felix Hoffmann re-synthesized it at Bayer in 1897, and the company launched it as "Heroin" in 1898 — marketed as a non-addictive cough suppressant and morphine substitute.[3] Addiction liability became undeniable within a decade.
Prohibition
The United States banned heroin outright in 1924, including all medical use.[3] The 1961 UN Single Convention on Narcotic Drugs placed it in Schedule I, establishing the international prohibition still in force today.[4] The United Kingdom diverged: diamorphine has remained licensed for medical use throughout, classified as a Class A, Schedule 2 substance.[1]
Heroin-assisted treatment
Switzerland launched supervised injectable heroin treatment in 1994 for severely dependent, treatment-resistant individuals.[9][10] Randomized trials in the Netherlands, Germany, Spain, Canada, and the United Kingdom confirmed better outcomes than methadone maintenance.[11] As of 2026, heroin-assisted treatment is available in eight countries; the United States does not permit it.
The trade name "Heroin" derives from the German heroisch (heroic) — how early test subjects described its effects.[3] South-west Asian heroin (dominant in European markets) is a brown free-base powder requiring acidification to inject; South-east Asian heroin is a white hydrochloride salt, directly water-soluble.[1] "Black tar" heroin, produced primarily in Mexico, is a crude dark form with variable purity.
Chemistry[edit]
Heroin (diacetylmorphine) belongs to the morphinan structural class — the same family as morphine and codeine. Its molecular formula is C₂₁H₂₃NO₅.
It is the diacetyl ester of morphine: two acetyl groups replace the hydroxyl groups on the morphine molecule, dramatically increasing fat-solubility and enabling rapid brain entry.[12] It is a semi-synthetic compound derived from morphine, which comes from the opium poppy (Papaver somniferum), and functions as a prodrug — the body converts it to more active compounds before it acts on opioid receptors.
Pharmacology[edit]
Mechanism of action
Heroin is a prodrug. Enzymes in the blood rapidly convert it to 6-monoacetylmorphine (6-MAM), which is further metabolized to morphine.[2] Both activate opioid receptors, suppressing pain signals, activating the brain's reward system, and depressing the brainstem's breathing drive.
6-MAM — not morphine — drives the initial rush. It produces a rapid biphasic brain response: first a drop in brain oxygen from respiratory depression, then a rise from vessel dilation.[13] Morphine sustains the effects over the hours that follow.
Pharmacokinetics
After intravenous injection, heroin crosses the blood-brain barrier within approximately 20 seconds, with roughly 70% of the dose reaching the brain.[1] This far exceeds morphine's brain penetration and explains why heroin produces a more intense rush.[2] Intranasal use delivers about 52% of the equivalent intramuscular dose.[14]
The conversion from heroin to 6-MAM happens in the blood — not the liver — and is fast: roughly 70% converts within 3 minutes.[15] Because major liver enzymes are not involved, drug-drug interactions at the metabolic level are limited.[15]
Neuroscience[edit]
Where it acts
Heroin's active metabolites activate opioid receptors on neurons in the brain's reward circuit, releasing dopamine and producing euphoria.[13] A separate pathway through the brainstem suppresses pain signals at their first relay point in the spinal cord. The lethal mechanism — respiratory depression — results from opioid suppression of the brain's breathing rhythm generators.
Tolerance and dependence
With repeated use, opioid receptors across multiple brain regions become less responsive.[7] Euphoria fades faster than respiratory tolerance — users chase lost pleasure with higher doses while the margin between intoxication and fatal overdose continues to narrow.
Over time, the drive to use shifts. The brain develops a countervailing dysphoria — anxiety, discomfort — that dominates when the drug wears off. Use becomes compulsive not to feel good, but to avoid feeling bad.
Whether the rapid 6-MAM-mediated reward signal creates stronger dependence than equivalent morphine has not been tested in controlled human studies. How fully heroin-induced brain changes reverse with abstinence is unclear — protracted withdrawal lasting months suggests incomplete recovery. Whether fentanyl, which now displaces heroin in many markets, produces different neuroadaptive patterns is an urgent open question.
Subjective Effects[edit]
Heroin's defining quality is what it removes. Pain disappears. Anxiety lifts. The body settles into a weighted, enveloping warmth that makes distress feel irrelevant. The onset is abrupt and total — an overwhelming wave of calm that erases discomfort at once. The plateau that follows is one of heavy, quiet sedation.
Compared to morphine, heroin produces a faster and more intense onset because it enters the brain more efficiently. Compared to fentanyl, the effects last considerably longer — three to five hours rather than thirty to sixty minutes — with a more gradual offset.
Synthesized by C.R. Alder Wright in 1874 and commercialized by Bayer in 1898 as a cough suppressant,[3] heroin was marketed as a non-addictive morphine alternative — a claim that proved catastrophically wrong. International prohibition led to UN Schedule I classification in 1961,[4] though randomized trials across six countries have since validated heroin-assisted treatment for refractory dependence.[5] In North America, illicitly manufactured fentanyl has largely displaced heroin in unregulated markets since 2021.[6]
Subjective effects include profound analgesia, euphoria, sedation, and anxiolysis. The experience is defined by its onset — a rapid, enveloping wave of warmth and heavy calm that erases physical pain and emotional distress, distinguishing it from the slower build of morphine. Nausea, respiratory slowing, severe constipation, and pronounced itching are characteristic unsought effects.
Heroin produces rapid physical dependence and carries the lowest margin of exposure of any commonly used substance.[7] Tolerance to euphoria develops via µ-opioid receptor desensitization[8] faster than tolerance to respiratory depression, narrowing the already thin safety margin; mortality among untreated dependent persons reaches 36.1 per 1000 person-years.[9] A century of clinical and forensic data underpin current understanding, though no controlled human dose-finding studies exist.
History[edit]
Discovery
Diacetylmorphine was first synthesized in 1874 by C.R. Alder Wright at St. Mary's Hospital Medical School in London, produced by boiling morphine with acetic anhydride.[3] The compound attracted little notice until Felix Hoffmann independently re-synthesized it at Bayer AG in 1897. Bayer's pharmacologist Heinrich Dreser recognized its antitussive potential and launched it commercially in 1898 under the trade name "Heroin," marketing it as a non-addictive substitute for morphine and codeine.[3]
Prohibition
Addiction liability became undeniable within a decade of commercial release. The United States imposed the first federal opiate controls through the Harrison Narcotics Tax Act of 1914, then banned heroin outright — including medical use — with the Anti-Heroin Act of 1924.[3] The 1961 UN Single Convention on Narcotic Drugs placed heroin in Schedule I, establishing the international prohibition framework that remains in force.[4] The United Kingdom diverged: diamorphine has remained licensed for medical use throughout, classified as a Class A, Schedule 2 substance.[1]
Heroin-assisted treatment
Switzerland pioneered clinical rehabilitation when it launched the PROVE programme in 1994 — supervised injectable diacetylmorphine for severely dependent, treatment-resistant individuals.[10][11] Subsequent randomized controlled trials in the Netherlands, Germany, Spain, Canada, and the United Kingdom confirmed sustained reductions in illicit use and superior retention compared to methadone maintenance.[5] As of 2026, heroin-assisted treatment is legally available in eight countries; the United States does not permit it.
The trade name "Heroin" derives from the German heroisch (heroic), a reference to how early test subjects described the compound's effects.[3] The name outlived Bayer's trademark and became the universal street term — an unusual case of a pharmaceutical brand name surviving its own prohibition.
Chemistry[edit]
Structural class
Diacetylmorphine belongs to the morphinan structural class — specifically the 4,5-epoxymorphinan subgroup shared by morphine, codeine, and hydromorphone. It is the 3,6-diacetyl ester of morphine: both hydroxyl groups on the morphine molecule are replaced with acetyl groups. This modification dramatically increases lipid solubility compared to morphine, enabling the rapid blood-brain barrier penetration that defines heroin's pharmacological character.
The compound is classified as a semi-synthetic opioid — derived from the natural alkaloid morphine (isolated from Papaver somniferum opium poppy latex) via chemical acetylation. Structurally, it sits between morphine and the fully synthetic opioids (fentanyl, methadone).
Molecular properties
| Molecular formula | C₂₁H₂₃NO₅ |
| Molecular weight | 369.4 g/mol |
The molecule contains the characteristic morphinan pentacyclic ring system: a phenanthrene nucleus fused with a piperidine ring and an oxygen bridge. The two acetyl ester groups at C-3 and C-6 are the sole structural difference from morphine and account for the compound's enhanced lipid solubility and prodrug behaviour.[12]
Stereochemistry
Diacetylmorphine possesses five chirality centres, all derived from the natural (−)-morphine precursor. Only the natural (−)-enantiomer is pharmacologically active at opioid receptors. The rigid pentacyclic framework prevents epimerization under physiological conditions — the stereochemistry is locked in place by the fused ring system.
Physical forms
The physical form encountered depends on geographic origin and salt form. South-west Asian heroin (predominant in European markets) exists as a brown free-base powder requiring acidification for injection. South-east Asian heroin is a white hydrochloride salt, directly water-soluble.[1] Both forms share identical pharmacology once dissolved.[12]
The free base melts at 173°C. The hydrochloride salt is water-soluble, making it suitable for injection without acidification.
Pharmacology[edit]
Mechanism of action
Diacetylmorphine functions primarily as a prodrug. After administration, enzymes in the blood and brain rapidly strip one acetyl group to produce 6-monoacetylmorphine (6-MAM), which is further converted to morphine. Morphine is then metabolized in the liver to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G).[2]
This sequential activation produces heroin's distinctive temporal profile. 6-MAM — not morphine — is the primary driver of the rapid onset effects. Studies using brain oxygen sensors in rats confirmed that 6-MAM produces the biphasic neural response characteristic of heroin (respiratory depression followed by cerebral vasodilation), while morphine alone produces only weak effects.[13]
All active metabolites work through the same target: the µ-opioid receptor. Activation hyperpolarizes neurons, reduces cellular signaling activity, and inhibits calcium channels. The net result is suppressed pain signaling (analgesia), activation of reward circuitry (euphoria), and depression of brainstem breathing centres (respiratory depression).
Pharmacokinetics
Absorption and onset
Following intravenous injection, diacetylmorphine crosses the blood-brain barrier within approximately 20 seconds, with nearly 70% of the dose reaching the brain.[1] This rapid penetration — far exceeding morphine's — is the pharmacokinetic basis for heroin's distinctive rush.
Both heroin and 6-MAM are substantially more lipid-soluble than morphine, enabling faster and more complete passage into the brain.[1][2] Intranasal bioavailability is approximately 52% relative to intramuscular administration.[14]
Metabolism
The metabolic pathway proceeds in three steps: heroin is converted to 6-MAM by blood esterases (not liver enzymes), 6-MAM is converted to morphine by further deacetylation, and morphine is processed in the liver to M3G and M6G.[2] No major liver enzymes (cytochrome P450) are involved in the heroin-to-morphine conversion — a clinically relevant distinction that limits drug-drug interactions at the metabolic level.[15]
Heroin's plasma half-life is concentration-dependent: 1.2–1.7 minutes at high concentrations, increasing to approximately 20 minutes at low concentrations.[15] At concentrations reached shortly after intravenous injection, approximately 70% converts to 6-MAM within 3 minutes.
Forensic detection
6-MAM is the definitive biomarker distinguishing heroin from morphine administration, detectable in vitreous humor in 100% of confirmed heroin-related deaths.[16] Opium alkaloid impurities — papaverine, noscapine, and codeine — serve as additional markers of illicit heroin use.[16]
Neuroscience[edit]
Where it acts
Heroin's active metabolites — 6-MAM and morphine — activate µ-opioid receptors on inhibitory neurons in the ventral tegmental area (VTA), releasing dopamine into the nucleus accumbens. This dopamine surge produces the acute reinforcement experienced as euphoria. The rapid biphasic neural signature of intravenous heroin — an initial drop in brain oxygen from respiratory depression, followed by a rise from cerebral vasodilation — is driven by 6-MAM, not morphine.[13]
Analgesia operates through a separate pathway: µ-opioid activation in the periaqueductal gray activates descending pain-suppression projections to the spinal cord, blocking pain signals at their first relay point. Respiratory depression — the lethal mechanism — results from suppression of breathing rhythm generators in the brainstem.
Tolerance and dependence
Chronic heroin use desensitizes µ-opioid receptor signaling in anatomically specific regions — the periaqueductal gray (reducing analgesia), the locus coeruleus (producing rebound effect anxiety during withdrawal), and brainstem respiratory centres (permitting dose escalation).[8] This regional pattern explains why different aspects of tolerance develop at different rates: users escalate doses chasing lost euphoria while respiratory tolerance lags behind.
The opponent-process model captures the broader trajectory: early use is driven by positive reinforcement (euphoria), but neuroadaptive countermeasures progressively strengthen a dysphoric rebound. With chronic exposure, the rebound dominates — use shifts from seeking pleasure to avoiding withdrawal, a transition that defines compulsive dependence.
Several questions remain unresolved. Whether the rapid 6-MAM-mediated reward signal drives greater abuse liability than equivalent morphine exposure has not been tested in controlled human studies. The degree to which heroin-induced brain changes reverse with sustained abstinence is unclear — protracted withdrawal symptoms lasting months suggest incomplete recovery.
Subjective Effects[edit]
Heroin's experiential character is shaped by a temporal cascade unique among opioids: the rapid 6-MAM-mediated rush (seconds, intravenous or smoked) gives way to sustained morphine-driven warmth and sedation over hours. Route of administration determines not just intensity but qualitative character — intravenous and smoked routes produce an acute euphoric surge absent from insufflated or oral use. Set and setting modulate the anxiolytic and sedative dimensions, but tolerance state is the dominant modifier, transforming the experience from overwhelming euphoria in a naive user to baseline maintenance in a dependent one.
Compared to Morphine, heroin produces a faster, more intense onset with a distinctive rush attributable to 6-MAM's superior brain penetration. Compared to fentanyl, heroin's effects are longer-lasting (3–5 hours versus 30–60 minutes intravenous) with a more gradual offset, though the contemporary drug supply has largely collapsed this distinction in North American markets.
Effect Grid
At common doses, the full opioid experience manifests: pronounced euphoria (the characteristic "rush" if injected or smoked, developing over seconds), deep physical and psychological warmth, potent analgesia, and significant anxiolysis. A pervasive sense of wellbeing and indifference to concerns dominates consciousness. Sedation is marked — the classic "nodding" (oscillating between wakefulness and light sleep) may begin at the upper end of this range.
Physically, miosis is pronounced, pruritus is common (particularly face and nose), nausea and vomiting occur in some users, and constipation is reliable. Respiratory depression is clinically meaningful — respiratory rate and tidal volume decrease. Skin flushing and peripheral vasodilation produce visible warmth.
Functional impairment is substantial. Driving and complex tasks are unsafe. Duration 3-5 hours with residual sedation extending further.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Spatial disorientation · Visual acuity suppression · Visual haze / noise · Auditory distortion · Visual processing suppression · Internal hallucinations
Visual processing suppression · Internal hallucinations
Constipation · Tactile euphoria · Bodily heaviness · Body high · Breathing alteration · Muscle relaxation · Physical fatigue · Appetite suppression · Spontaneous body sensations · Nausea · Sexual arousal suppression · Excessive sweating · Dizziness · Dry mouth · Nasal congestion · Temperature dysregulation · Vomiting · Dehydration sensation · Heart rate perception changes · Tingling / electric sensations · Abnormal heartbeat · Watery eyes · Involuntary body movements · Bodily dissociation
Body high · Breathing alteration · Muscle relaxation · Physical fatigue · Appetite suppression · Spontaneous body sensations · Nausea · Sexual arousal suppression · Excessive sweating · Dizziness · Dry mouth · Nasal congestion · Vomiting · Dehydration sensation · Heart rate perception changes · Tingling / electric sensations · Abnormal heartbeat · Watery eyes · Involuntary body movements · Bodily dissociation
Information processing suppression · Thought deceleration · Focus suppression · Motivation suppression · Analysis suppression · Language suppression · Immersion enhancement · Memory suppression · Confusion · Memory fragmentation · Suggestibility enhancement · Thought disorganization · Cognitive dysphoria · Delusions of sobriety · Amnesia · Delirium
Motivation suppression · Analysis suppression · Language suppression · Immersion enhancement · Memory suppression · Confusion · Memory fragmentation · Thought disorganization · Cognitive dysphoria · Delusions of sobriety · Amnesia · Delirium
Disinhibition · Depersonalization · Derealization · Cognitive disconnection
Timeline
First effects perceived within 10-60 seconds of insufflation as diacetylmorphine absorbs through nasal mucosa. Onset is slower than IV but substantially faster than oral opioids.
Effects build steadily over 5-15 minutes. Warmth, mood elevation, and analgesia develop progressively. The rush is less intense than IV due to slower absorption and ~52% relative bioavailability.
Sustained peak of euphoria, sedation, analgesia, and anxiolysis. Nodding may occur at higher doses. Respiratory depression present but typically less acute than IV peak.
Gradual decline as morphine is metabolized. Sedation lifts, warmth fades, and baseline awareness returns. Duration somewhat longer than IV due to continued mucosal absorption.
Residual drowsiness, mild analgesia, and constipation. Cognitive slowing may persist.
⚠ Do not drive or operate machinery for at least 6 hours after insufflation due to residual CNS depression and impaired reflexes.
Safety[edit]
- Acute toxicity
- Critical
- Chronic toxicity
- High
- Withdrawal
- Severe
- Tolerance buildup
- rapid
- Tolerance reset
- 10 days
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- High
- Cross-tol.
- morphine · oxycodone · fentanyl
Toxicity
Acute toxicity
The primary fatal mechanism is respiratory depression — the brainstem's breathing drive is suppressed, oxygen drops, and breathing stops. Clinically meaningful slowed breathing occurs in the majority of users at standard doses.[17] At a benchmark dose of 2 mg/kg, heroin has the lowest safety margin of any commonly used substance.[6]
All-cause mortality among opioid-dependent people out of treatment reaches 36.1 per 1000 person-years; overdose-specific mortality is 12.7 per 1000 person-years.[8]
Tolerance loss and overdose risk
Chronic toxicity
Prolonged use causes serious physical harm. White matter brain deterioration can develop with any route of use.[18][19] Injection adds further risks: heart valve infection (infective endocarditis), blood poisoning, HIV and hepatitis C from shared needles,[20][21] skin abscesses, and tetanus.[20]
Heroin crosses the placenta, causing a 6-fold increase in obstetric complications and a 74-fold increase in sudden infant death syndrome.[22] Children born to dependent mothers show decreased cognition and language deficits.[23] Abrupt cessation during pregnancy carries fetal risk; managed opioid agonist therapy is preferred over detoxification.[22]
Adulterant hazards
Psychological risks
Heroin use disorder is one of the most severe forms of substance dependence. Use is driven first by euphoria, then by the compulsive need to avoid withdrawal. Co-occurring depression, anxiety, PTSD, and personality disorders are common — both as risk factors and as consequences of chronic use.
Chronic use impairs decision-making and impulse control, though this may partially improve with sustained abstinence. Heroin does not cause acute psychotic episodes or perceptual disturbances. The psychological harms are those of dependence, not acute intoxication.
Tolerance and dependence
Tolerance develops as opioid receptors across multiple brain regions become less sensitive.[7] This crosses to all µ-opioid agonists — morphine, oxycodone, Fentanyl, methadone, and hydromorphone are all affected.
Physical dependence develops within days to weeks of continuous use. Withdrawal includes anxiety, restlessness, muscle pain, nausea, vomiting, diarrhea, and rapid heart rate — beginning 6–24 hours after last use, peaking at 36–72 hours, and resolving over 5–10 days. Dysphoria, anhedonia, and sleep disturbance may persist for weeks to months. Buprenorphine effectively manages acute withdrawal.[24]
Drug Interactions
The defining hazard is additive respiratory depression. When heroin combines with other CNS depressants, multiple mechanisms suppress breathing simultaneously, and the combined effect exceeds either drug alone. Benzodiazepines are the most common co-ingestant in opioid fatalities.[25] Alcohol, GHB/GBL, ketamine, and tramadol carry the same additive risk; tramadol also lowers the seizure threshold, making the combination potentially fatal.
Naloxone reverses opioid-induced respiratory depression by blocking opioid receptors. Its duration of action is 30–90 minutes — shorter than heroin's — requiring observation for re-sedation or repeated dosing. Naloxone does not reverse xylazine effects.
Contraindications
8 knownAny pre-existing respiratory condition — COPD, severe asthma, sleep apnoea — narrows the gap between effective and lethal doses. Active benzodiazepine, alcohol, or sedative use is an absolute contraindication due to additive respiratory depression. Severe liver disease prolongs active morphine metabolites, increasing accumulation and overdose risk.
Pregnancy is a contraindication to unsupervised heroin use; heroin crosses the placenta and dramatically increases obstetric complications.[22] Head injury is also a contraindication — opioids raise intracranial pressure and mask neurological deterioration. After any period of abstinence, tolerance decays rapidly; resuming at previous doses is a leading cause of fatal overdose.safety citation needed
Harm Reduction[edit]
Forms & Identification
Near-total contamination of North American street heroin with fentanyl has made testing essential before every use. Fentanyl test strips detect presence but not concentration — a negative result reduces risk but does not eliminate it, since fentanyl distribution within a sample is often uneven.
Brown powder (free base) requires acidification to dissolve for injection — this step affects the final concentration. White powder (hydrochloride) dissolves directly in water. Both are visually indistinguishable from fentanyl powder without chemical testing.
Guidelines
- Test every batch with fentanyl test strips before use
- Start with a fraction of the intended dose ("test shot") — potency varies unpredictably between batches and even within the same batch
- Keep naloxone within arm's reach of anyone present
- Never use alone — respiratory depression is survivable with intervention, fatal without it
- After any period of abstinence (days to weeks), assume tolerance has decayed significantly and reduce dose accordingly
- Use sterile equipment for every injection — new needle, new cooker, new filter, new water
- Eat before using — nausea and vomiting while sedated risk aspiration
Set & Setting
Never use alone. The primary acute danger — respiratory depression — is survivable if someone is present to administer naloxone and call emergency services. A trusted person who is not using, who knows where naloxone is and how to use it, is the single most important risk reduction measure.
A calm, familiar environment reduces anxiety-driven dose escalation. Avoid using when exhausted, ill, or in emotional crisis — these states lower the respiratory depression threshold.
Aftercare & integration. Aftercare for heroin centres on physical recovery and honest self-assessment — not psychological integration.
After use, prioritize hydration and nutrition. Opioids suppress appetite and slow digestion; constipation may persist for days. Monitor for signs of developing dependence: using more than intended, using to avoid feeling bad, needing more for the same effect. If use is becoming regular, this is the critical intervention window — speak with a healthcare provider about opioid agonist therapy before physical dependence is entrenched.
Recovery & Support
Heroin dependence is a treatable medical condition. The most effective interventions are opioid agonist therapies — buprenorphine (Suboxone, Subutex) and methadone — which stabilize brain chemistry, prevent withdrawal, reduce craving, and dramatically lower overdose mortality.[24] These are evidence-based treatments that restore function and save lives.
Naltrexone (extended-release injection) is an alternative for those who have completed detoxification and prefer an opioid-blocking approach, though retention rates are lower than agonist therapies.
Peer support (SMART Recovery, Narcotics Anonymous, local harm reduction organizations) provides community and accountability. For those not ready to stop, harm reduction services — needle exchanges, supervised consumption sites, drug checking — reduce immediate risk while maintaining a pathway to treatment.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Slow or stopped breathing, blue or grey lips and fingertips, gurgling or snoring sounds, pinpoint pupils, unresponsive to voice or pain — any of these indicate opioid overdose.
Immediate steps:
- 1. Call emergency services immediately
- 2. Administer naloxone (intranasal or intramuscular) — repeat every 2–3 minutes if no response
- 3. Place the person in the recovery position (on their side) to prevent choking
- 4. Perform rescue breathing if trained: one breath every 5 seconds
- 5. Stay with the person — naloxone wears off in 30–90 minutes and re-sedation can occur
- 6. Do NOT put anything in their mouth, do NOT put them in cold water, do NOT try to keep them awake by causing pain
What to tell the dispatcher: "Someone is not breathing / breathing very slowly. I think it's an opioid overdose. I've given naloxone." State the address, how many people are affected, and what substances may be involved. Good Samaritan laws in many jurisdictions protect people who call for help during an overdose.
Reversal agent: Naloxone reverses opioid-induced respiratory depression but does NOT reverse xylazine effects. If xylazine is suspected (common in North American supply), respiratory support and emergency medical care remain essential even after naloxone administration.
Legal Status[edit]
Heroin is among the most strictly controlled substances in the world, illegal for production, possession, and trade in all UN signatory states except under narrow medical or scientific authorization.[4]
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule I (Controlled Substances Act, 1970) | No accepted medical use; possession and distribution are federal felonies. Heroin-assisted treatment is not permitted[26] |
| United Kingdom | Class A, Schedule 2 (Misuse of Drugs Act 1971) | Schedule 2 permits medical prescribing (diamorphine); possession carries a maximum of 7 years; trafficking carries a maximum of life imprisonment. Heroin-assisted treatment is legally available[1] |
| Canada | Schedule I (Controlled Drugs and Substances Act, 1996) | Maximum 7 years imprisonment for possession (indictable); life for trafficking. Limited heroin-assisted treatment programmes operate under Section 56 exemptions[27] |
| Australia | Schedule 9 — Prohibited Substance | Most severe scheduling category; possession and supply are criminal offences with state-level penalties[27] |
| Germany | BtMG Annex I | Unauthorized possession and trafficking are criminal offences; penalties up to 5–15 years. Heroin-assisted treatment has been legal since 2009[27] |
| Switzerland | Special federal authorization | Heroin-assisted treatment is permanently established as a national programme; supervised injectable diacetylmorphine is available for treatment-resistant opioid use disorder[9] |
Safety[edit]
- Acute toxicity
- Critical
- Chronic toxicity
- High
- Withdrawal
- Severe
- Tolerance buildup
- rapid
- Tolerance reset
- 10 days
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- High
- Cross-tol.
- morphine · oxycodone · fentanyl
Toxicity
Acute toxicity
The primary mechanism of fatal heroin overdose is respiratory depression — suppression of the brainstem's breathing drive leading to oxygen deprivation and respiratory arrest. Clinically meaningful slowed breathing occurs in the majority of users at standard doses; monitoring in supervised injection settings observed hypoventilation in 8 of 10 patients within 30 minutes.[18]
Heroin's benchmark dose of 2 mg/kg bodyweight represents the lowest margin of exposure of any substance in comparative risk assessments, placing it in the highest-risk category.[7] All-cause mortality among opioid-dependent persons out of treatment reaches 36.1 per 1000 person-years, with overdose-specific mortality at 12.7 per 1000 person-years.[9]
Tolerance loss and overdose risk
Chronic toxicity
White matter brain damage (toxic leukoencephalopathy): Progressive white matter deterioration classically associated with heroin inhalation ("chasing the dragon") but documented with injected and insufflated routes.[19][20] Prognosis ranges from recovery to death.
Injection-related infections: Heart valve infection (infective endocarditis, primarily right-sided, from Staphylococcus aureus and Candida species),[21] HIV and hepatitis C transmission via needle sharing,[22] blood poisoning, skin abscesses, and tetanus.[21]
Lung damage: Fluid in the lungs (non-cardiogenic pulmonary edema) during acute overdose, aspiration pneumonia, septic emboli, and granulomatous disease from injected adulterants (talc, cotton fibres).
Pregnancy risks: Heroin crosses the placenta. Opioid-dependent pregnant women face a 6-fold increase in obstetric complications (low birth weight, fetal distress, meconium aspiration) and a 74-fold increase in sudden infant death syndrome.[23] Long-term effects on exposed children include decreased cognition and language deficits.[24] Abrupt cessation during pregnancy carries fetal risk; managed opioid agonist therapy (methadone or buprenorphine) is preferred over detoxification.[23]
Adulterant hazards
Psychological risks
Heroin use disorder represents one of the most severe forms of substance dependence. The psychological profile is dominated by compulsive use driven first by positive reinforcement (euphoria) and later by negative reinforcement (avoidance of withdrawal). High prevalence of co-occurring depression, anxiety disorders, PTSD, and personality disorders — both as risk factors and consequences — characterizes the dependent population.
Chronic opioid use is associated with deficits in executive function, decision-making, and impulse control, potentially reversible with sustained abstinence. Unlike serotonergic psychedelics, heroin does not produce acute psychotic episodes, perceptual disturbances, or HPPD. The psychological harms are those of dependence, not acute intoxication.
Tolerance and dependence
Tolerance develops via µ-opioid receptor desensitization across multiple brain regions — periaqueductal gray, locus coeruleus, brainstem respiratory centres, thalamus, and amygdala.[8] Receptor uncoupling and cellular counter-adaptations (upregulation of opposing signaling pathways) compound this effect. Tolerance is cross-tolerant to all µ-opioid receptor agonists (morphine, oxycodone, Fentanyl, Methadone, hydromorphone).
Physical dependence develops within days to weeks of continuous use. The withdrawal syndrome includes anxiety, restlessness, muscle pain, tearing, runny nose, goosebumps, nausea, vomiting, diarrhea, and rapid heart rate. Onset is typically 6–24 hours after last use, peaking at 36–72 hours, with acute symptoms resolving over 5–10 days. Protracted withdrawal — dysphoria, anhedonia, sleep disturbance, and craving — may persist for weeks to months.
Buprenorphine is effective for managing acute opioid withdrawal.[25] Methadone maintenance prevents withdrawal through continuous receptor occupancy. Non-opioid adjuncts (clonidine, lofexidine) provide symptomatic relief of the adrenergic rebound effect.
Drug Interactions
The defining interaction hazard is additive respiratory depression with other central nervous system depressants — multiple agents suppressing brainstem breathing drive produce effects greater than either alone.
Benzodiazepines are among the most common co-ingestants in opioid fatalities.[26] They potentiate GABA-mediated sedation while heroin metabolites suppress opioid-mediated breathing drive. This combination is the single most common pharmacological contributor to heroin overdose death apart from opioid dose itself.
Alcohol produces additive respiratory and central nervous system depression. Frequently documented in heroin overdose fatalities.
GHB/GBL combines a different sedative mechanism with opioid respiratory depression, producing dangerous additive effects with loss of protective airway reflexes.
Tramadol presents dual risk: opioid effects produce additive respiratory depression, while its additional pharmacology lowers the seizure threshold. The combination is potentially fatal.
Ketamine compounds sedation and respiratory depression risk in combination.
Naloxone is the critical therapeutic interaction — it competitively blocks µ-opioid receptors, reversing heroin-induced respiratory depression. Its duration of action is shorter than heroin's (30–90 minutes), requiring observation for re-sedation or repeated dosing. Naloxone does not reverse xylazine effects.
Contraindications
8 knownRespiratory compromise: Any condition reducing baseline breathing capacity (COPD, severe asthma, sleep apnoea, obesity-related breathing impairment) narrows the margin between effective and lethal opioid doses. Pre-existing respiratory impairment is an absolute contraindication to unsupervised opioid use.
Concurrent sedative use: Active benzodiazepine, alcohol, or other sedative use is an absolute contraindication due to additive respiratory depression.
Pregnancy: Heroin crosses the placenta, producing neonatal withdrawal syndrome and dramatically increased obstetric complications.[23] Abrupt cessation during pregnancy carries fetal risk; managed opioid agonist therapy is preferred over detoxification.[23]
Liver impairment: Morphine processing is liver-dependent. Severe liver disease prolongs the active life of morphine and M6G, increasing accumulation and overdose risk.
Post-abstinence tolerance loss: Following any period of reduced use — incarceration, hospitalization, detoxification — tolerance decays rapidly. Resumption at previously tolerated doses is a leading cause of fatal overdose.safety citation needed
Head injury: Opioids increase pressure inside the skull via carbon dioxide retention from respiratory depression, and mask neurological deterioration through sedation.
Harm Reduction[edit]
Forms & Identification
The structured data module above shows reagent results, physical forms, and common adulterants. What that data means in practice: the near-total contamination of North American street heroin with fentanyl and xylazine has made testing essential before every use. Fentanyl test strips detect the presence but not the concentration of fentanyl — a negative result reduces risk but does not eliminate it, as fentanyl distribution within a sample is often uneven.
Brown powder (free base) requires acidification (typically citric acid) to dissolve for injection — this step introduces another variable affecting concentration. White powder (hydrochloride) dissolves directly in water. Both forms are visually indistinguishable from fentanyl powder without testing.
Guidelines
- Test every batch with fentanyl test strips before use
- Start with a fraction of the intended dose ("test shot") — potency varies unpredictably between batches and even within the same batch
- Keep naloxone within arm's reach of anyone present
- Never use alone — respiratory depression is survivable with intervention, fatal without it
- After any period of abstinence (days to weeks), assume tolerance has decayed significantly and reduce dose accordingly
- Use sterile equipment for every injection — new needle, new cooker, new filter, new water
- Eat before using — nausea and vomiting while sedated risk aspiration
Set & Setting
Never use alone. The primary acute danger — respiratory depression — is survivable if someone is present to administer naloxone and call emergency services. A trusted person who is not using, who knows where naloxone is and how to use it, is the single most important risk reduction measure.
A calm, familiar environment reduces anxiety-driven dose escalation. Avoid using when exhausted, ill, or in emotional crisis — these states lower the respiratory depression threshold.
Aftercare & integration. Opioid use does not typically produce the kind of experience that benefits from psychological integration in the psychedelic sense. Aftercare for heroin centres on physical recovery and honest self-assessment.
After use, prioritize hydration and nutrition — opioids suppress appetite and slow digestion. Constipation may persist for days; fibre and adequate water intake help. Monitor for signs of developing dependence: using more than intended, using to avoid feeling bad rather than to feel good, and needing more to achieve the same effect. If use is becoming regular, this is the critical intervention window — speak with a healthcare provider about opioid agonist therapy options before physical dependence is entrenched.
Recovery & Support
Heroin dependence is a treatable medical condition. The most effective interventions are opioid agonist therapies — buprenorphine (Suboxone, Subutex) and methadone — which stabilize brain chemistry, prevent withdrawal, reduce craving, and dramatically lower overdose mortality.[25] These are not "replacing one drug with another" — they are evidence-based treatments that restore function and save lives.
Naltrexone (extended-release injection) is an alternative for those who have completed detoxification and prefer an opioid-blocking approach, though retention rates are lower than agonist therapies.
Peer support programmes (SMART Recovery, Narcotics Anonymous, local harm reduction organizations) provide community and accountability. Many people in sustained recovery credit the combination of medication and peer support as more effective than either alone. For those not ready to stop, harm reduction services — needle exchange programmes, supervised consumption sites, drug checking — reduce the immediate risks of continued use while maintaining a pathway to treatment.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Slow or stopped breathing, blue or grey lips and fingertips, gurgling or snoring sounds, pinpoint pupils, unresponsive to voice or pain — any of these indicate opioid overdose.
Immediate steps:
- 1. Call emergency services immediately
- 2. Administer naloxone (intranasal or intramuscular) — repeat every 2–3 minutes if no response
- 3. Place the person in the recovery position (on their side) to prevent choking
- 4. Perform rescue breathing if trained: one breath every 5 seconds
- 5. Stay with the person — naloxone wears off in 30–90 minutes and re-sedation can occur
- 6. Do NOT put anything in their mouth, do NOT put them in cold water, do NOT try to keep them awake by causing pain
What to tell the dispatcher: "Someone is not breathing / breathing very slowly. I think it's an opioid overdose. I've given naloxone." State the address, how many people are affected, and what substances may be involved. Good Samaritan laws in many jurisdictions protect people who call for help during an overdose.
Reversal agent: Naloxone reverses opioid-induced respiratory depression but does NOT reverse xylazine effects. If xylazine is suspected (common in North American supply), respiratory support and emergency medical care remain essential even after naloxone administration.
Legal Status[edit]
International framework
Heroin is listed in Schedule I of the 1961 United Nations Single Convention on Narcotic Drugs, making its production, possession, and trade illegal in all signatory states except under strict medical or scientific authorization.[4] This framework has remained essentially unchanged since 1961, though individual nations have developed divergent approaches to medical use and harm reduction.
Most jurisdictions impose maximum or near-maximum penalties for trafficking and significant penalties for possession.
Jurisdictions
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule I (Controlled Substances Act, 1970) | No accepted medical use; possession and distribution are federal felonies. Heroin-assisted treatment is not permitted[27] |
| United Kingdom | Class A, Schedule 2 (Misuse of Drugs Act 1971) | Schedule 2 permits medical prescribing (diamorphine); possession carries a maximum of 7 years; trafficking carries a maximum of life imprisonment. Heroin-assisted treatment is legally available[1] |
| Canada | Schedule I (Controlled Drugs and Substances Act, 1996) | Maximum 7 years imprisonment for possession (indictable); life for trafficking. Limited heroin-assisted treatment programmes operate under Section 56 exemptions[28] |
| Australia | Schedule 9 — Prohibited Substance | Most severe scheduling category; possession and supply are criminal offences with state-level penalties[28] |
| Germany | BtMG Annex I | Unauthorized possession and trafficking are criminal offences; penalties up to 5–15 years. Prosecutorial discretion applies for small-quantity possession. Heroin-assisted treatment has been legal since 2009[28] |
| Switzerland | Special federal authorization | Heroin-assisted treatment is permanently established as a national programme; supervised injectable diacetylmorphine is available for treatment-resistant opioid use disorder[10] |
Medical use exceptions
The United Kingdom and Switzerland represent the most significant exceptions to global prohibition. In the UK, diamorphine maintains Schedule 2 classification permitting medical prescription — used for acute pain management and heroin-assisted treatment under specialist supervision.[1] Switzerland's PROVE programme (1994–present) demonstrated that clinical heroin provision is compatible with public health objectives, influencing policy adoption in the Netherlands, Germany, Denmark, Belgium, Norway, and Canada.[10][5]
Frequently asked questions
What is Heroin?
Heroin is a semi-synthetic opioid and prodrug of the morphinan class, first synthesized in 1874 and acting via mu-opioid receptor agonism. Sequential deacetylation produces 6-MAM and morphine; high lipophilicity enables blood-brain barrier penetration within seconds of intravenous injection.
How long does Heroin last?
Total duration by route of administration — Intravenous: 3 – 5 hours; Insufflated: 4 – 6 hours; Smoked: 3 – 5 hours. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for Heroin?
Psychedex publishes a dosage table for Heroin on this page covering these routes of administration: intravenous, insufflated, smoked. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with Heroin?
The highest-severity documented interactions for Heroin: Benzodiazepines, Barbiturates (Lethal), GHB, Baclofen (Lethal), GHB, GBL (Lethal), Local anesthetics (Lethal), 5-HTP, Tryptophan (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is Heroin addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for Heroin: tolerance builds rapid; full reset takes 10 days; cross-tolerance develops with morphine, oxycodone, fentanyl, methadone, hydromorphone, codeine, buprenorphine. See the article's dependence and safety sections for recorded dependence data.
experience reports
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First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
- [1]
- [2] ^abcMilella MS, D'Ottavio G, De Pirro S, Barra M, Caprioli D, Badiani A (2023) Heroin and its metabolites: relevance to heroin use disorder — Translational Psychiatry doi:10.1038/s41398-023-02406-5
- [3]
- [4] ^abcCsete J, Kamarulzaman A, Kazatchkine M, et al. (2016) Public health and international drug policy — The Lancet doi:10.1016/s0140-6736(16)00619-x
- [5] ^abRussell E, Sisco E, Thomson A, et al. (2023) Rapid Analysis of Drugs: Pilot Surveillance System to Detect Changes in the Illicit Drug Supply - Eight Syringe Services Programs, Maryland, 2021-2022 — MMWR Morbidity and Mortality Weekly Report doi:10.15585/mmwr.mm7217a2
- [6] ^abLachenmeier DW, Rehm J (2015) Comparative risk assessment of alcohol, tobacco, cannabis and other illicit drugs using the margin of exposure approach — Scientific Reports doi:10.1038/srep08126
references
- [1]
- [2] ^abcdMilella MS, D'Ottavio G, De Pirro S, Barra M, Caprioli D, Badiani A (2023) Heroin and its metabolites: relevance to heroin use disorder — Translational Psychiatry doi:10.1038/s41398-023-02406-5
- [3]
- [4] ^abcCsete J, Kamarulzaman A, Kazatchkine M, et al. (2016) Public health and international drug policy — The Lancet doi:10.1016/s0140-6736(16)00619-x
- [5] ^abcStrang J, Groshkova T, Uchtenhagen A, et al. (2015) Heroin on trial: systematic review and meta-analysis of randomised trials of diamorphine-prescribing as treatment for refractory heroin addiction — British Journal of Psychiatry doi:10.1192/bjp.bp.114.149195
- [6] ^abRussell E, Sisco E, Thomson A, et al. (2023) Rapid Analysis of Drugs: Pilot Surveillance System to Detect Changes in the Illicit Drug Supply - Eight Syringe Services Programs, Maryland, 2021-2022 — MMWR Morbidity and Mortality Weekly Report doi:10.15585/mmwr.mm7217a2