What are the properties, uses, and considerations of heroin (diamorphine)?

Heroin (Diamorphine)

Heroin is an illicit, highly addictive semi-synthetic opioid with no legitimate therapeutic use in the United States, though it is used medically in the UK for specific indications including myocardial infarction, palliative care, and severe acute pain; in clinical practice, it represents a high-alert substance of abuse with profound risks of addiction, overdose, and death. 1, 2, 3

Drug Classification

Generic name: Heroin (Diacetylmorphine, Diamorphine) 2, 3

Brand name: None in US; used as "Diamorphine" in UK medical practice 3

Drug class: Schedule I controlled substance (US); Opioid agonist 2

Route: Intravenous (most common), intranasal, subcutaneous, intramuscular, smoking, oral 2, 4

High alert: YES - Extreme risk for addiction, overdose, and death 1, 2, 5

Mechanism of Action

Heroin functions as a prodrug that rapidly crosses the blood-brain barrier and is metabolized to 6-acetylmorphine and morphine, which bind to mu opioid receptors (MORs) in the brain and spinal cord to produce analgesia, euphoria, and respiratory depression. 1, 6

• Heroin itself has minimal opioid receptor activity but is rapidly deacetylated to active metabolites 1
• The combined effect of morphine and 6-acetylmorphine metabolites accounts for heroin's high relative potency compared to other opioids 1
• Peak plasma concentrations of 6-acetylmorphine occur within 5-10 minutes after intranasal administration, with morphine peaking within 1 hour 4
• Opioids reduce pain perception rather than blocking pain transmission, leaving sensory pathways intact while altering subjective pain interpretation 1, 6
• MORs in the brainstem respiratory center (pre-Bötzinger complex) mediate life-threatening respiratory depression 6

Therapeutic Uses

In the United States, heroin has NO approved medical uses and is classified as Schedule I. 2

In the United Kingdom, diamorphine is used for: 3

• Myocardial infarction (acute coronary syndrome) 3
• Palliative care for severe pain 3
• Pulmonary edema 3
• Post-operative pain management 3
• Heroin-assisted treatment for treatment-resistant severe addiction (experimental) 5, 7

Adverse Effects

The primary life-threatening adverse effect is respiratory depression leading to respiratory arrest and death, with mortality rates among heroin users between 1-3% annually. 8, 2, 5

Serious/Life-Threatening Effects:

• Respiratory depression, apnea, respiratory arrest 8, 2
• Circulatory depression, shock, cardiac arrest 8
• Overdose death (especially after periods of abstinence due to loss of tolerance) 2, 5
• Anaphylactoid reactions (rare) 8
• Cardiovascular instability 8

Common Effects:

• Sedation, drowsiness, somnolence 8
• Euphoria ("rush" or "high") followed by dysphoria 8, 2
• Nausea, vomiting, constipation 8
• Lightheadedness, dizziness 8
• Diaphoresis (sweating) 8
• Miosis (pinpoint pupils) 8
• Pruritus, urticaria, flushing (histamine release) 8

Neurological:

• Confusion, disorientation, delirium 8
• Transient hallucinations 8
• Impairment of mental and physical performance 8
• Seizures 8

Cardiovascular:

• Orthostatic hypotension, syncope 8
• Bradycardia or tachycardia 8
• Peripheral circulatory collapse 8

Genitourinary:

• Urinary retention or hesitancy 8
• Reduced libido and potency 8

Long-term Medical Consequences:

• Scarred and collapsed veins 2
• Bacterial infections of blood vessels and heart valves 2
• Liver and kidney disease 2
• Lung complications including pneumonia 2
• HIV, hepatitis B and C (from needle sharing) 2

Endocrine:

• Adrenal insufficiency (with chronic use >1 month) 8
• Androgen deficiency 8

Physical Dependence and Withdrawal

Physical dependence develops with repeated high-dose administration, manifesting as withdrawal symptoms within hours of the last dose, with major symptoms peaking at 48-72 hours and subsiding after approximately one week. 2

Withdrawal Symptoms Include: 2

• Restlessness and insomnia 2
• Intense drug craving 2
• Diarrhea 2
• Severe muscle and bone pain 2
• Cold flashes with piloerection ("goose bumps") 2
• Involuntary leg movements 2
• Pronounced weakness and depression 2
• Nausea and vomiting 2

Some chronic users demonstrate persistent withdrawal signs for months or years after cessation. 2

Opioid receptor re-sensitization typically occurs within 3-7 days after discontinuation, with complete resolution of tolerance, physical dependence, and hyperalgesia generally occurring within one week. 6

Addiction Profile

Heroin is considered the most addictive opioid, though addiction following regular use occurs in less than 25% of persons who ever try it; however, for those who develop addiction, it frequently becomes a chronic relapsing disease. 2, 5

Addiction Characteristics: 2

• Compulsive drug use despite harmful consequences 2
• High tendency to relapse after periods of abstinence 2
• Powerful drug craving or "heroin hunger" with significant motivational significance 2
• The addiction state does not resolve promptly like tolerance and physical dependence 6

Route and Addiction Risk:

• Intravenous administration is the predominant method and indicates more serious addiction 2
• Recent shift from injection to sniffing and smoking observed 2
• Rapid delivery to the brain (IV, intranasal) produces stronger reward and higher addiction potential 6

Nursing Assessment

Immediate assessment priorities focus on respiratory status, level of consciousness, pupil size, and vital signs, with particular attention to signs of overdose or withdrawal. 8, 2

Respiratory Assessment:

• Monitor respiratory rate, depth, and oxygen saturation continuously 8
• Assess for respiratory depression (rate <12 breaths/minute) 8
• Evaluate for apnea or irregular breathing patterns 8
• Have naloxone immediately available for overdose reversal 8

Neurological Assessment:

• Level of consciousness (sedation to coma) 8
• Pupil size (miosis/pinpoint pupils indicate opioid effect) 8
• Mental status (confusion, disorientation, hallucinations) 8
• Seizure activity 8

Cardiovascular Assessment:

• Blood pressure (assess for hypotension, orthostatic changes) 8
• Heart rate (bradycardia or tachycardia) 8
• Signs of circulatory collapse or shock 8
• Peripheral perfusion 8

Injection Site Assessment (if applicable):

• Inspect for track marks, scarred veins 2
• Assess for local tissue irritation, pain, induration 8
• Evaluate for signs of infection (cellulitis, abscess) 2
• Check for phlebitis 8

Withdrawal Assessment:

• Onset of symptoms (typically within hours of last use) 2
• Severity of symptoms (peak at 48-72 hours) 2
• Vital sign instability 2
• Gastrointestinal symptoms (diarrhea, nausea, vomiting) 2
• Musculoskeletal pain 2
• Psychiatric symptoms (anxiety, depression, drug craving) 2

Risk Assessment:

• History of substance use disorders 9
• Multiple prescribers or "doctor shopping" 9
• Psychiatric comorbidities 9
• Risk factors for infectious diseases (HIV, hepatitis) 2
• Suicidal ideation (particularly during withdrawal or early recovery) 2

Aberrant Behaviors to Monitor: 9

• Requesting early refills or escalating dosages (most common concerning behavior) 9
• Taking more medication than prescribed 9
• Reports of lost or stolen medications 9
• Unremitting focus on obtaining controlled substances 9

Contraindications

Absolute contraindications include known hypersensitivity to opioids, significant respiratory depression, acute or severe bronchial asthma in unmonitored settings, and known or suspected gastrointestinal obstruction. 8

Specific Contraindications:

• Hypersensitivity to diamorphine, morphine, or other opioid agonists 8
• Significant respiratory depression 8
• Acute or severe bronchial asthma in unmonitored settings 8
• Known or suspected paralytic ileus or gastrointestinal obstruction 8

Use with Extreme Caution in:

• Patients with chronic obstructive pulmonary disease or cor pulmonale 8
• Decreased respiratory reserve 8
• Hypoxia, hypercapnia 8
• Pre-existing respiratory depression 8
• Cardiovascular instability 8
• Patients with acute ulcerative colitis (risk of toxic megacolon) 8
• Concurrent benzodiazepine or CNS depressant use (increased risk of respiratory depression and death) 8

Clinical Considerations

Overdose Risk:

Risk for overdose is greatest during the first 3-7 days after opioid initiation or dose increase, and is dramatically elevated after periods of abstinence due to loss of tolerance. 6, 2

• Tolerance to analgesia develops faster than tolerance to respiratory depression, increasing overdose risk 6
• An overdose can be lethal following heroin use after a period of abstinence (voluntary or involuntary) 2, 5
• Mortality rate among heroin users is 1-3% annually 5

Drug Interactions:

Concurrent use with benzodiazepines or other CNS depressants dramatically increases risk of profound sedation, respiratory depression, and death. 8

• Opioids delay gastrointestinal motility, potentially reducing absorption and effectiveness of oral antiplatelet agents (e.g., clopidogrel) in acute coronary syndrome 1
• Serotonergic drugs increase risk of serotonin syndrome 8

Tolerance and Hyperalgesia:

• Tolerance develops through molecular and circuit-level adaptations in opioid receptors 6
• Opioid-induced hyperalgesia can develop even after a few administrations 6
• Cross-tolerance between opioids may require higher doses for adequate pain control 6

Pregnancy and Neonatal Effects:

• Chronic maternal use causes neonatal opioid withdrawal syndrome 8
• Neonatal withdrawal can be life-threatening if not recognized and treated 8

Public Health Context:

In 2019,745,000 individuals in the US used heroin, with 404,000 using both heroin and misusing prescription opioids, representing a shift from prescription opioids to cheaper, more accessible illicit opioids. 1

• Increased difficulty obtaining prescription opioids has led to increased heroin use 1
• Heroin is increasingly laced with synthetic opioids like fentanyl, dramatically increasing overdose risk 1
• Heroin-related deaths continue to rise despite leveling of prescription opioid deaths 1

Treatment Approaches:

Methadone and buprenorphine for opioid use disorder increase retention in treatment and decrease illicit opioid use, with effectiveness enhanced when combined with psychosocial treatments. 1, 7

• Buprenorphine/naloxone combination tablets reduce diversion potential 7
• Heroin-assisted treatment may be considered for treatment-resistant severe addiction 5, 7
• Alpha-2 adrenergic agonists can reduce withdrawal symptoms 7

Critical Pitfalls to Avoid

• Never abruptly discontinue in physically dependent patients - taper slowly to avoid precipitating severe withdrawal 6
• Do not underestimate overdose risk after abstinence - tolerance is lost within days, making previous doses potentially lethal 6, 2
• Avoid patient abandonment when aberrant behaviors emerge - reassess treatment plan and consider broad differential diagnosis including inadequate analgesia, tolerance, or psychiatric comorbidity 9
• Do not assume respiratory depression tolerance parallels analgesic tolerance - respiratory depression risk persists even as analgesic effects diminish 6
• Never prescribe opioids without assessing for concurrent benzodiazepine use - combination dramatically increases mortality risk 8