Key Highlights
  • Heroin is a semi-synthetic opioid derived from morphine, which comes from the opium poppy
  • Classified as a Schedule I substance — no accepted medical use and high abuse potential
  • Rapidly converts to morphine in the brain, producing intense euphoria ("the rush")
  • Available as a white or brown powder or a sticky black substance (black tar heroin)
  • Can be injected, smoked, or snorted — injection carries highest overdose and disease risk
  • Approximately 1.1 million Americans reported heroin use in the past year (2021)
  • Heroin addiction develops rapidly due to the drug's fast onset and intense euphoria
  • Treatment includes medication-assisted therapy with methadone, buprenorphine, or naltrexone

Published: February 2026 | Last Updated: February 2026 | Reading Time: 7 min

What Is Heroin?

Heroin (diacetylmorphine) is a semi-synthetic opioid originally synthesized from morphine in 1874 by English chemist C.R. Alder Wright. Morphine itself is a naturally occurring alkaloid extracted from the seed pods of the opium poppy plant (Papaver somniferum). Heroin was commercially introduced by the pharmaceutical company Bayer in 1898, originally marketed as a non-addictive alternative to morphine — a claim that proved tragically inaccurate.

Legal Classification

Heroin is classified as a Schedule I controlled substance under the U.S. Controlled Substances Act, meaning it has no currently accepted medical use, lacks accepted safety parameters for use under medical supervision, and has a high potential for abuse. Unlike other opioids such as morphine, oxycodone, or fentanyl, heroin cannot be legally prescribed in the United States.

Forms and Appearance

Heroin is found in several forms depending on its geographic origin and purity. East Coast heroin (from South America or Southeast Asia) is typically a fine white or off-white powder. Mexican heroin may appear as a brown powder or as "black tar heroin" — a dark, sticky, tar-like substance with lower purity. The form and appearance affect the methods of use, purity, and the types of adulterants and cutting agents present.

How Heroin Affects the Brain and Body

Mechanism of Action

After entering the body, heroin is rapidly metabolized into morphine and 6-monoacetylmorphine (6-MAM). These active metabolites bind to mu-opioid receptors concentrated in brain regions involved in pain perception, reward, and respiratory control. The heroin molecule's lipophilicity (fat solubility) allows it to cross the blood-brain barrier faster than morphine, producing its characteristically rapid and intense onset.

The Rush

The immediate sensation after heroin use, particularly when injected, is described as an intense wave of euphoria known as "the rush." This is accompanied by warmth, heaviness in the extremities, dry mouth, and a profound sense of well-being. The rush results from rapid flooding of opioid receptors and a massive surge in dopamine release.

Subsequent Effects

Following the initial rush, users experience several hours of alternating wakefulness and drowsiness ("nodding"), clouded mental function, slowed heart rate and breathing, and suppressed pain signals. Nausea and vomiting are common, particularly in new users.

Health Consequences

Overdose

Heroin overdose is a leading cause of death among drug users. Opioids suppress the brainstem's respiratory drive, and excessive doses can slow or stop breathing entirely. Signs of overdose include pinpoint pupils, slow or absent breathing, blue-tinged lips or fingernails, loss of consciousness, and limp body. The adulterant fentanyl — increasingly mixed into heroin supplies — has dramatically increased overdose risk.

Injection-Related Complications

Intravenous heroin use carries specific risks including transmission of blood-borne infections (HIV, hepatitis B and C), bacterial endocarditis (heart valve infection), abscesses and soft tissue infections, collapsed veins (track marks), and necrotizing fasciitis.

Long-Term Effects

Chronic heroin use causes constipation, hormonal imbalances, cognitive impairment, deterioration of white matter in the brain affecting decision-making and stress regulation, and increased risk of mental health disorders including depression and antisocial personality disorder.

Heroin Addiction

Why Heroin Is Highly Addictive

Several factors make heroin one of the most addictive substances. The speed and intensity of onset create powerful neurological reinforcement. Tolerance develops rapidly, requiring escalating doses. Withdrawal is acutely uncomfortable, motivating continued use. And the neuroadaptive changes in the brain's reward and stress systems create a persistent vulnerability to relapse.

Withdrawal

Heroin withdrawal typically begins 6-12 hours after the last dose and peaks at 2-3 days. Symptoms include severe muscle and bone pain, insomnia, diarrhea, vomiting, cold flashes with goosebumps ("cold turkey"), restless legs, and intense cravings. While heroin withdrawal is rarely life-threatening, the extreme discomfort drives many individuals to relapse.

Treatment for Heroin Addiction

Evidence-based treatment for heroin use disorder combines medication-assisted treatment (MAT) with behavioral therapies. The three FDA-approved medications for opioid use disorder are methadone (a full opioid agonist that eliminates withdrawal and cravings), buprenorphine (a partial agonist that reduces cravings with lower overdose risk), and naltrexone (an opioid antagonist that blocks euphoric effects). Behavioral therapies including cognitive-behavioral therapy and contingency management address the psychological dimensions of addiction.

Frequently Asked Questions

Is heroin the same as morphine?

Heroin (diacetylmorphine) is derived from morphine and rapidly converts back to morphine in the body. However, heroin's chemical structure allows it to cross the blood-brain barrier faster, producing a more intense and rapid onset than morphine administered by the same route.

Can you overdose from smoking heroin?

Yes. While injection carries the highest overdose risk due to the entire dose entering the bloodstream at once, fatal overdoses also occur from smoking and snorting heroin — particularly when it is laced with fentanyl.

How does heroin addiction usually start?

Many individuals who develop heroin addiction first misuse prescription opioids. When prescription opioids become difficult or expensive to obtain, some individuals transition to heroin, which produces similar effects at a lower cost. Approximately 80% of people who use heroin first misused prescription opioids.

Is heroin addiction curable?

Heroin addiction is considered a chronic, manageable condition. With medication-assisted treatment and behavioral therapy, individuals can achieve sustained recovery. Some patients benefit from long-term or indefinite medication maintenance, similar to managing other chronic conditions.

References

  1. National Institute on Drug Abuse. (2024). Heroin DrugFacts.
  2. Centers for Disease Control and Prevention. (2023). Heroin Overdose Data.
  3. Substance Abuse and Mental Health Services Administration. (2023). Medications for Opioid Use Disorder.
  4. Cicero, T.J., et al. (2014). The changing face of heroin use in the United States. JAMA Psychiatry.
  5. Drug Enforcement Administration. (2023). Heroin.

This article was reviewed by the Valley Spring Recovery Center Editorial Team. For more information about heroin addiction treatment, call (201) 781-8812 or visit our admissions page.

Valley Spring Recovery Center — Evidence-based addiction treatment in Norwood, New Jersey.