Heroin

Description

Heroin is the popular name for diamorphine. It acts as a depressant, so it slows down functions and reactions in the body and is also a strong pain killer (analgesic). Discovered in 1874, it comes from the opium poppy.

Heroin can be a highly dependence-forming drug, producing tolerance to its effects and deep physical dependence—without it the user becomes ill and unable to function normally. It should also be noted that the drug is especially effective at reducing psychological and emotional pain, and most people dependent on heroin can be accurately described as people self-medicating against traumatic memories and intolerable feelings. The time taken to become dependent varies with the individual and context, as does the severity of withdrawal symptoms. Overdose can be fatal, of course, and most overdoses are due to profound depression of the respiratory system. After many years of abundant supply at user-end purity, in the UK heroin quality now varies significantly.

Pharmaceutical grade heroin is called diacetylmorphine or diamorphine. ‘Heroin’ refers to the illicit type, originating from the Golden Triangle (Thailand, Laos and Myanmar) and is usually (off) white. Most of the heroin available in the UK comes from The Golden Crescent (Afghanistan, Iran and Pakistan), and is a base form of the drug (an intermediary stage in the production process to the salt form). This makes it suitable for smoking, and much illicit heroin is smoked on tin-foil (‘chasing the dragon’ or ‘booting’).

The salt form of diamorphine/heroin is very soluble, and the base (usually a brown powder) can also be injected, but requires an acidifier and heat to make it dissolve (citric acid or vitamin C typically). For more advice, including harm reduction, see our safer injecting guidance.

Pharmacology

Heroin is a relatively weak opioid itself and instead mainly acts as an opioid pro-drug: after efficiently crossing the blood-brain barrier, it is rapidly metabolised into the more potent µ-opioid agonists 6-monoacetylmorphine (6-MAM) and morphine, which then bind to opioid receptors resulting in the drug’s euphoric, anxiolytic (reducing anxiety), and painkilling effects.

Prolonged heroin use can lead to desensitisation and downregulation of the µ-opioid receptors, requiring higher doses to achieve the same effects. If after repeated use the individual suddenly stops ‘cold turkey’, they will have fewer, less responsive opioid receptors, leading to a reduction in the body’s response to endorphins which causes withdrawal symptoms or ‘dope sickness’. This can leave people feeling worse than they did prior to using heroin and may cause physical dependence, resulting in further use in an attempt to alleviate withdrawal.

Taking heroin in combination with other depressants dramatically increases the risk of fatal overdose. Drinking alcohol or taking benzodiazepines, Z-drugs, or gabapentinoids alongside heroin causes compounding sedation and slows breathing to dangerous levels. Naloxone is an opioid antagonist that reverses the effects of an opioid overdose; to find out how naloxone works and where to get free kits, visit our Naloxone guidance page.

Harm Reduction

• Carry naloxone: Naloxone is an opioid antagonist that reverses an overdose. Several counterfeit pills and street heroin batches across the UK have been found to contain highly potent synthetic opioids (such as nitazenes). Carry naloxone and make sure people around you know how to use it. Visit our Naloxone page to find out how to get free kits.
• Be extremely careful mixing: Mixing heroin with other depressants (alcohol, benzodiazepines, gabapentinoids, methadone) multiplies overdose risk exponentially rather than additively. Avoid mixing whenever possible, or reduce your doses substantially.
• Test your stuff: You cannot tell purity, cutting agents, or synthetic opioid contamination by sight. Send a small sample for free, anonymous testing to WEDINOS, or pick up rapid test strips from our Harm Reduction Hub.
• Start low and go slow: Always take a small test dose first, especially with a new batch or after a period of abstinence when tolerance drops quickly.
• Try not to use alone: If you overdose, someone needs to be there to administer naloxone and call 999. If using with others, stagger your doses so at least one person is alert.
• Be mindful of location-conditioned tolerance: Tolerance is partially conditioned to your familiar environment. When using in an unfamiliar location, your tolerance may be lower, making overdose more likely.
• Safer injecting practices: Always use new, sterile injecting equipment from a local Needle and Syringe Programme (NSP). Never share needles, syringes, spoons, filters, or water. Find your nearest NSP on our Local Services page.
• Nutrition and health: Heroin suppresses appetite; ensure you eat regular meals and stay hydrated. Heroin also suppresses libido and can disrupt the menstrual cycle.
• Treatment & substitution options: If you are looking for support or stability, Opioid Substitution Therapy (OST with methadone or buprenorphine) is available through local services. Learn more on our Local Services page or call our Helpline.

History

While the synthesis of diacetylmorphine dates to 1874 (first synthesised by C.R. Alder Wright in Paddington, London, and commercially launched in 1899 by Bayer in Germany under the trademark ‘Heroin’), opium itself has a millennia-long history of social and medical use.

The prohibition and criminalisation of opium in the early 20th century inadvertently accelerated the adoption of heroin as a more concentrated, easily trafficked alternative. This shift replaced traditional cultural contexts with a rapid black market and introduced injecting as a cost-effective administration method, bringing severe public health consequences including blood-borne virus transmission and escalating overdose rates.

For decades, the UK pioneered the controlled prescribing of pharmaceutical diamorphine to dependent individuals under what became known internationally as ‘The British System’. Today, diamorphine remains a licensed prescription medicine in the UK for severe pain and palliative care, while specialist doctors require a Home Office licence to prescribe it for opioid dependence.

Law

Class A under the Misuse of Drugs Act 1971.
Schedule 2 under the Misuse of Drugs Regulations 2001.

Possible offences

• Possession: Maximum sentence of up to 7 years imprisonment, an unlimited fine, or both.
• Possession With Intent To Supply (PWITS): Maximum sentence of up to life imprisonment, an unlimited fine, or both.
• Supply: (including being concerned in supply, conspiracy to supply, aggravated supply, and offer to supply) Maximum sentence of up to life imprisonment, an unlimited fine, or both.
• Production: Maximum sentence of up to life imprisonment, an unlimited fine, or both.

In practice, maximum sentences are rarely imposed, particularly for simple possession. For detailed guidance on sentencing guidelines and thresholds, visit our Drugs Law & Rights section.