Diamorphine (heroin)
Drugs of abuse
Drugs of abuse
Heroin: an opioid made from morphine. A rush, then drowsiness and slowed breathing; overdose kills by respiratory arrest and responds to naloxone.
Also called: Heroin, Diacetylmorphine
Quick facts
- Group
- Drugs of abuse
- Target
- Mu-opioid receptor (after conversion to morphine)
- Used for
- Clinical relevance · Clinical relevance
- Key effects
- Rush with warm flushing of the skin · Nausea
- Monitor
- Airway · Pupils and response to naloxone · Temperature
- ATC
- N07BC06
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows morphine, into which heroin is converted in the brain, bound to the human mu-opioid receptor with its Gi protein.
Diamorphine is morphine with two acetyl groups, which make it more fat-soluble, so it enters the brain faster than morphine. There it is converted to morphine (via 6-monoacetylmorphine), which activates mu-opioid receptors. The fast rise gives an intense 'rush'. Mu receptors in the limbic system reinforce use; in the spinal cord they block pain; in the brainstem they depress the response to carbon dioxide, so breathing slows and can stop.
- Fat-soluble: crosses into the brain very fast
- Converted to morphine there
- Mu-opioid receptors: rush, reward, analgesia
- Brainstem: breathing slows and may stop
Indications
- Clinical relevance: opioid overdose with coma, pinpoint pupils and slow breathing Opioid overdose →
- Clinical relevance: opioid use disorder Opioid use disorder, overdose and withdrawal →
Adverse effects
Common
- Rush with warm flushing of the skin, dry mouth and heavy limbs
- Nausea, vomiting, severe itching
- Drowsiness and clouded thinking ('nodding')
- Constipation, insomnia; irregular periods and sexual dysfunction with chronic use
Contraindications
- No safe non-medical use
- Especially dangerous with alcohol, benzodiazepines or other sedatives, after a period of abstinence (lost tolerance), or when mixed with unknown adulterants
Key interactions
- Alcohol, benzodiazepines and other CNS depressants
- Deeper sedation and respiratory depression.
- Naloxone
- Rapidly reverses the opioid effects, including breathing depression; it can also precipitate withdrawal.
- Naltrexone
- Blocks opioid effects; used in treatment after detoxification.
What is monitored
- Airway, breathing rate, oxygen saturation and level of consciousness
- Pupils and response to naloxone; re-sedation as naloxone wears off
- Temperature, injection sites, heart murmurs (endocarditis)
- HIV, hepatitis B and C testing
Pregnancy and breastfeeding
Use in pregnancy can cause neonatal abstinence syndrome; methadone or buprenorphine with prenatal care improves outcomes for mother and baby.
Nursing care
- Support breathing first (bag-mask ventilation, oxygen), then give naloxone as ordered.
- Observe after naloxone: its effect can end before the opioid's, and breathing can slow again.
- Treat withdrawal symptoms and offer medicines for opioid use disorder (methadone, buprenorphine, naltrexone).
- Teach naloxone use to family and friends; refer for testing and harm reduction.
Pharmacokinetics
- Absorption
- Injected, smoked or snorted; white or brown powder or sticky 'black tar'.
- Metabolism
- Rapidly converted to 6-monoacetylmorphine and morphine.
- Onset and duration
- The rush comes within moments when injected or smoked; drowsiness lasts several hours.
Test yourself
Think of the answer, then tap the question to see it.
Why does heroin reach the brain faster than morphine?
Its two acetyl groups make it more fat-soluble; in the brain it is converted back to morphine.
What is the classic triad of opioid overdose?
Coma, pinpoint pupils and respiratory depression.
Why must a patient be watched after naloxone reverses a heroin overdose?
Naloxone may wear off before the opioid does, and breathing can slow again.
Which infections are linked to sharing injection equipment?
HIV and hepatitis B and C (also bacterial endocarditis and abscesses from injection).
Connections
← Back to the class: Drugs of abuse
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: What are the immediate (short-term) effects of heroin use? (National Institute on Drug Abuse (NIDA), 2026); What are the medical complications of chronic heroin use? (National Institute on Drug Abuse (NIDA), 2026); What can be done for a heroin overdose? (National Institute on Drug Abuse (NIDA), 2026); How does heroin use affect pregnant women? (National Institute on Drug Abuse (NIDA), 2026).
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Representative model, for educational purposes only.