Conditions · Emergency medicine and toxicology

Salicylate (aspirin) toxicity !

Poisoning by aspirin or other salicylates. It causes ringing ears, fast breathing and a dangerous acid-base disturbance.

Updated 2026-11-01

Structures involved

Tap one to see what it is and open it in 3D.

Why it happens

What it is

Poisoning from an acute overdose or chronic excess of aspirin or other salicylates (including methyl salicylate in oil of wintergreen and topical products). It causes a mixed acid-base disorder and can affect the brain, lungs and kidneys.

Who gets it

Less frequent than in the past as paracetamol has replaced aspirin for many uses, but still seen in intentional overdoses and in chronic toxicity in older adults taking aspirin regularly. Aspirin is widely sold without prescription in Latin America.

Causes

Acute intentional or accidental ingestion of aspirin tablets
Chronic therapeutic excess, especially in older adults
Methyl salicylate (oil of wintergreen) or salicylate-containing ointments and remedies
Enteric-coated or large ingestions forming tablet masses (bezoars) that delay absorption

Risk factors

Depression and self-harm
Older age, kidney impairment and dehydration (chronic toxicity)
Young children with access to medicines or topical products
Use of several salicylate-containing products at once

Pathophysiology

Salicylates directly stimulate the medullary respiratory centre, causing early respiratory alkalosis. They also uncouple oxidative phosphorylation and disturb metabolism, causing an anion-gap metabolic acidosis, heat production and glucose depletion in the brain. Acidaemia lets more non-ionised drug enter the brain, worsening toxicity; increased capillary permeability can cause pulmonary and cerebral oedema.

Classification

Acute versus chronic toxicity
Mild, moderate or severe according to clinical features and acid-base status

Symptoms and signs

Tinnitus and decreased hearing
Nausea, vomiting and epigastric pain
Fast, deep breathing (tachypnoea, hyperpnoea)
Sweating, fever and dehydration
Agitation, confusion or lethargy

Diagnosis

Clinical: History of ingestion and the combination of tinnitus, vomiting, hyperventilation and altered mental status. Chronic toxicity in older adults is easily mistaken for sepsis or delirium.
Tests: Serial serum salicylate levels until falling, arterial or venous blood gases (respiratory alkalosis with anion-gap metabolic acidosis), electrolytes and anion gap, glucose, kidney function, coagulation, and a paracetamol level to exclude co-ingestion.
Imaging: Chest X-ray if pulmonary oedema is suspected; head CT if consciousness is reduced for another reason.

Differential diagnosis

Sepsis or diabetic ketoacidosis
Methanol or ethylene glycol poisoning (anion-gap acidosis)
Paracetamol or other drug overdose
Delirium from other causes in older adults
Heat stroke

Goal of treatment

Prevent further absorption, enhance elimination by alkalinising the urine, correct fluid, potassium and glucose, and arrange haemodialysis for severe poisoning.

Treatment

Acute: Activated charcoal when the airway is protected and the ingestion is recent; repeated doses may be considered for delayed or enteric-coated absorption.
Medical: Intravenous fluids and sodium bicarbonate to alkalinise serum and urine, with potassium replacement because hypokalaemia prevents urinary alkalinisation; glucose for altered mental status.
Procedure: Haemodialysis for altered mental status, kidney failure, pulmonary oedema, very high or rising levels, or worsening acidosis despite treatment.
Follow-up: Frequent salicylate levels, blood gases, potassium, glucose and urine pH; if intubation is unavoidable, ventilation is set to keep the patient's high minute ventilation.

Complications

Non-cardiogenic pulmonary oedema
Cerebral oedema, seizures and coma
Acute kidney injury
Gastrointestinal bleeding
Hypoglycaemia in the brain despite normal blood glucose
Death

Prognosis

Most mild to moderate cases recover with alkalinisation and supportive care. Chronic toxicity diagnosed late, older age, neurological signs and acidaemia carry a higher mortality.

Prevention

Child-resistant packaging and safe storage of medicines and topical products
Review of aspirin use and kidney function in older adults
Screening for suicide risk

Test yourself

Think of the answer, then tap the question to see it.

What acid-base disorder is typical of adult salicylate poisoning?

A mixed respiratory alkalosis (direct respiratory centre stimulation) and anion-gap metabolic acidosis.

Which early symptom is characteristic of salicylate toxicity?

Tinnitus (ringing in the ears), often with nausea, vomiting and hyperventilation.

Why must potassium be corrected when alkalinising the urine?

With hypokalaemia the kidney retains potassium and excretes hydrogen ions, so the urine cannot be alkalinised.

What are two indications for haemodialysis in salicylate toxicity?

Altered mental status and kidney failure; also pulmonary oedema, very high levels or refractory acidosis.

Why is intubation dangerous in salicylate poisoning?

Losing the patient's own hyperventilation causes rapid acidaemia, driving salicylate into the brain and causing deterioration.

Add to my cards (5)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Aspirin overdose (MedlinePlus, US National Library of Medicine, 2026).

← All conditions

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.

Medulla oblongata highlighted on the Durgical 3D model