Drug overdose

Specialties > Emergency medicine and intensive care

Background knowledge 🧠

Definition

A drug overdose occurs when an individual takes a quantity of a substance greater than the recommended or generally practiced dose, leading to a toxic effect on the body.
It can be intentional (e.g., suicide attempt) or unintentional (e.g., accidental ingestion).
Overdoses can involve prescription medications, illicit drugs, over-the-counter medications, or alcohol.

Epidemiology

Drug overdose is a significant public health issue in the UK, contributing to thousands of deaths annually.
Opioids are the most common drugs involved in overdose deaths.
Incidence is higher in individuals aged 35-49 years and among those with a history of substance abuse or mental health disorders.
Certain regions, such as Scotland, have higher overdose mortality rates.

Aetiology and pathophysiology

Overdose can result from excessive consumption of drugs due to tolerance, dependence, or misuse.
Polypharmacy, especially in elderly patients, increases overdose risk.
Pathophysiological effects depend on the drug, e.g., respiratory depression with opioids, cardiac arrhythmias with stimulants.
Chronic use of drugs can alter metabolic pathways, leading to increased risk of overdose with usual doses.

Types

Opioid overdose: Most common and life-threatening due to respiratory depression.
Sedative overdose: Includes benzodiazepines and barbiturates, leading to CNS depression.
Stimulant overdose: Includes cocaine, amphetamines, causing hyperthermia, seizures.
Antidepressant overdose: Risk of arrhythmias, seizures, particularly with tricyclic antidepressants.
Alcohol overdose: Can lead to respiratory depression, aspiration, coma.
Paracetamol overdose: Common, causes hepatic failure if untreated.

Clinical Features 🌡️

Symptoms

Confusion, delirium, or altered mental state.
Nausea, vomiting, abdominal pain.
Breathing difficulties, such as shallow breathing or apnea.
Seizures or muscle spasms.
Cyanosis or other signs of hypoxia.

Signs

Reduced consciousness, coma.
Pinpoint pupils (opioid overdose).
Dilated pupils (stimulant overdose).
Hypotension or hypertension, depending on the substance.
Bradycardia or tachycardia.
Signs of trauma (e.g., head injury) due to falls or accidents during intoxication.
Track marks (injection drug users).

Investigations 🧪

Tests

Blood tests: FBC, U&E, LFTs, glucose, coagulation profile.
Toxicology screen: Urine and blood tests for common drugs.
ABG: Assess respiratory function and metabolic acidosis.
ECG: Identify arrhythmias or QT prolongation, especially in tricyclic antidepressant overdose.
Imaging: CXR if aspiration pneumonia is suspected.

Management 🥼

Management

Airway management: Ensure patency, consider intubation if needed.
Breathing: Oxygen supplementation, ventilatory support if required.
Circulation: IV fluids, vasopressors for hypotension.
Decontamination: Activated charcoal within 1 hour of ingestion if appropriate.
Antidotes: Naloxone for opioid overdose, flumazenil for benzodiazepine overdose.
Monitoring: Continuous observation in a high-dependency area.
Psychiatric evaluation: Post-recovery to assess suicide risk if intentional overdose.

Complications

Aspiration pneumonia.
Hypoxic brain injury.
Cardiac arrest.
Rhabdomyolysis leading to renal failure.
Hepatic failure (especially in paracetamol overdose).
Seizures.

Prognosis

Prognosis depends on the substance, dose, and time to treatment.
Timely intervention often leads to full recovery.
Delayed treatment, especially in cases of severe hypoxia or hepatic failure, can result in long-term complications or death.
Recurrent overdoses increase risk of cumulative damage.

Key points

Always assess and stabilize airway, breathing, and circulation first.
Consider the possibility of mixed overdoses and the need for multiple interventions.
Ensure safe and supportive monitoring environment during the acute phase.
Mental health assessment is crucial in cases of intentional overdose.

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