Key Facts

Opioid overdose is a leading cause of preventable death in the UK, particularly from illicit heroin and increasingly from fentanyl. Prompt recognition and naloxone administration are life-saving. Public health approaches including take-home naloxone and supervised consumption facilities are key prevention strategies.

Epidemiology

Opioid-related deaths have increased significantly over the past decade. Approximately 4,500 drug-related deaths per year in the UK (England, Wales, and Scotland combined), with opioids implicated in approximately 50-60%. Scotland has the highest drug death rate in Europe. Risk factors include male sex, social deprivation, periods after release from prison, and loss of tolerance.

Aetiology

• Illicit opioids: Heroin (diamorphine), fentanyl and analogues, methadone diversion
• Prescription opioids: Codeine, tramadol, dihydrocodeine, morphine, oxycodone, fentanyl patches
• OTC opioids: Co-codamol, codeine linctus
• Risk factors for overdose: IV injection, loss of tolerance (post-prison, post-detox), concurrent benzodiazepine/alcohol use, respiratory comorbidity, variable street drug purity

Pathophysiology

Opioids act on mu (μ), kappa (κ), and delta (δ) receptors. Mu-receptor activation in the brainstem depresses the respiratory centre, reducing respiratory rate and tidal volume. Hypoxia and hypercapnia progress to respiratory arrest. Additional effects include central sedation, miosis, reduced gut motility, nausea, histamine release, and hypotension.

Classic Triad

• Respiratory depression: RR <12/min; shallow breathing; apnoea
• Reduced consciousness: Drowsy → unresponsive (GCS ≤8)
• Miosis (pinpoint pupils): Bilateral; may be absent in severe hypoxia (dilated pupils) or mixed overdose

Additional Features

• Cyanosis, hypoxia (SpO2 <92%)
• Hypotension, bradycardia
• Hypothermia
• Track marks, injection sites (IV drug users)
• Pulmonary oedema (non-cardiogenic) — heroin-associated
• Needle still in situ

Red Flags

• RR <8/min or apnoea — immediate naloxone and ventilatory support
• GCS ≤8 — secure airway, recovery position, naloxone
• Fentanyl/carfentanil exposure — may need very high naloxone doses (10mg+)
• Body-packing (swallowed drug packages) — risk of massive release
• Mixed OD (opioid + benzodiazepine) — most common combination in fatal overdose
• Hypothermia — rhabdomyolysis risk from prolonged immobility

Bedside

• ABCDE assessment: Airway and breathing are priority
• SpO2 and respiratory rate: Continuous monitoring
• Blood glucose: Exclude hypoglycaemia
• GCS: Serial assessment
• Temperature: Hypothermia common
• ECG: QTc prolongation (methadone), arrhythmias

Bloods

• ABG/VBG: PaCO2 (elevated = hypoventilation), pH, lactate
• FBC, U&Es, LFTs: Baseline organ function
• CK: Rhabdomyolysis (prolonged immobility on hard surface)
• Paracetamol level: Always check — co-formulated opioids (co-codamol, co-dydramol)

Imaging

• CXR: If aspiration suspected or pulmonary oedema
• Abdominal X-ray/CT: If body-packing suspected

Special Tests

• Urine drug screen: Confirms opioid use but does NOT change acute management
• Naloxone response: Diagnostic and therapeutic — improvement confirms opioid toxicity

Non-pharmacological

• Airway management: Head tilt/chin lift, jaw thrust, recovery position
• Bag-valve-mask ventilation: If inadequate respiratory effort
• Intubation: If naloxone insufficient or prolonged respiratory failure

Pharmacological

Naloxone:

• IV route: 400mcg (0.4mg) IV; repeat every 2-3 min until adequate respiration (up to 10mg or more)
• IM/SC route: 800mcg (0.8mg) IM if no IV access; slower onset (~5 min)
• Intranasal: Nyxoid 1.8mg per nostril — community/pre-hospital
• Titration principle: Aim to restore adequate respiration (RR ≥12) NOT full consciousness — avoids precipitating severe withdrawal
• Naloxone infusion: Two-thirds of initial effective dose per hour in 5% glucose — for long-acting opioids (methadone, sustained-release preparations)

Monitoring post-naloxone:

• Observe minimum 2 hours after last naloxone dose for short-acting opioids
• Observe 6-12 hours (or longer) for methadone/sustained-release opioid overdose
• Watch for re-narcotisation when naloxone wears off

Surgical/Interventional

• Whole bowel irrigation: For body-packers (polyethylene glycol)
• Surgical retrieval: If body-packer with clinical toxicity or package rupture

Referral Criteria

• All overdoses — psychiatric assessment if intentional
• Drug and alcohol services — referral for opioid dependence (opiate substitution therapy)
• Take-home naloxone — provide to patient and family at discharge
• Safeguarding — children in household of opioid users

• With prompt naloxone: Excellent — full recovery expected in uncomplicated cases
• Without treatment: Respiratory arrest → cardiac arrest → death within minutes
• Complications: Aspiration pneumonia, non-cardiogenic pulmonary oedema, rhabdomyolysis (from immobility), anoxic brain injury (from prolonged hypoxia)
• Post-prison release: 7-8× increased risk of opioid death in first 2 weeks (loss of tolerance)
• Naloxone take-home programmes: Reduce opioid-related deaths by ~30-50% in target populations

Naloxone Dosing Guide

Observation Times Post-Naloxone

Take-Home Naloxone (UK)