Conditions · Emergency medicine and toxicology

Theophylline toxicity !

Poisoning by theophylline or aminophylline, asthma and COPD medicines with a narrow safe range. It causes vomiting, fast heart rhythms and seizures.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

Toxicity from theophylline or aminophylline, methylxanthine bronchodilators with a narrow therapeutic window. It occurs after acute overdose or, more dangerously, as chronic toxicity in older patients whose clearance falls. The hallmark is persistent vomiting, tachyarrhythmias, seizures and metabolic changes such as low potassium and high glucose.

Who gets it

Theophylline is now less used worldwide but remains in use for COPD and asthma in parts of Latin America, including Colombia, because it is inexpensive and oral. Chronic toxicity typically affects older adults with heart failure, liver disease or new interacting medicines; acute overdoses occur with extended-release tablets.

Causes

Intentional or accidental acute overdose, often of extended-release tablets
Chronic accumulation from reduced clearance
Interacting drugs that inhibit metabolism (some macrolides, fluoroquinolones such as ciprofloxacin, cimetidine, allopurinol)
Stopping smoking while on a stable dose (clearance falls)
Intravenous aminophylline given too fast

Risk factors

Older age
Heart failure, liver cirrhosis, viral illness with fever
New interacting drugs
Smoking cessation
Extended-release formulations in overdose

Pathophysiology

Theophylline blocks adenosine receptors and inhibits phosphodiesterase, raising cyclic AMP, and it stimulates catecholamine release. Excess causes beta-adrenergic overstimulation: sinus and supraventricular tachycardias, atrial fibrillation and ventricular arrhythmias, hypotension from beta-2 vasodilation, and intracellular shift of potassium with hyperglycaemia and lactic acidosis. Adenosine antagonism lowers the seizure threshold, and seizures are often prolonged. Vomiting arises from central stimulation and gastric irritation.

Classification

Acute overdose: high levels, marked vomiting, hypokalaemia, hyperglycaemia, arrhythmias
Chronic toxicity: lower levels can still cause seizures and arrhythmias, especially in older adults
Acute-on-chronic toxicity

Symptoms and signs

Persistent, often severe vomiting
Palpitations and fast heart rate
Restlessness, tremor, agitation and insomnia
Abdominal pain and diarrhoea
Seizures
Fast breathing and low blood pressure in severe cases

Diagnosis

Clinical: Ask about theophylline use, formulation, recent dose changes, smoking cessation and new medicines; look for vomiting, tachycardia, tremor and agitation.
Tests: Serum theophylline levels repeated every few hours until falling; potassium, glucose, magnesium, phosphate, lactate and blood gas; ECG with continuous monitoring; creatine kinase if there were seizures.
Imaging: Usually none; chest X-ray for aspiration and head CT if seizures have an unclear cause.

Differential diagnosis

Caffeine or other stimulant poisoning
Sympathomimetic poisoning (cocaine, amphetamines)
Thyroid storm
Salicylate toxicity
Sedative or alcohol withdrawal

Goal of treatment

Control vomiting, arrhythmias and seizures, correct metabolic changes and remove the drug quickly when levels or clinical severity are high.

Treatment

Acute: Repeated doses of activated charcoal (theophylline is enhanced by gut dialysis) once vomiting is controlled with antiemetics; benzodiazepines first-line for seizures, then barbiturates; phenytoin is avoided.
Medical: Short-acting beta-blockers for tachyarrhythmias and hypotension caused by beta-2 effects, used carefully in patients with bronchospasm; fluids and vasopressors for hypotension; cautious potassium replacement.
Procedure: Extracorporeal removal (haemodialysis preferred) for very high levels, seizures, life-threatening arrhythmias or failure to improve.
Follow-up: Continuous ECG, serial levels and electrolytes, neurological checks. Nursing: seizure precautions and aspiration precautions given vomiting.
Conservative: Review the indication; often switch to safer inhaled therapy for asthma or COPD and teach about interactions and smoking changes.

Complications

Status epilepticus with brain injury
Ventricular tachycardia and cardiac arrest
Rhabdomyolysis
Aspiration pneumonia
Severe hypokalaemia and lactic acidosis

Prognosis

Most patients recover with early charcoal and supportive care. Seizures signal a poor outlook, particularly in chronic toxicity in older adults, where they can occur at lower levels and are associated with high mortality.

Prevention

Level monitoring, dose adjustment for age and comorbidity, checking interactions before starting antibiotics or other drugs, and preferring inhaled therapies where possible

Test yourself

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

What two actions explain theophylline toxicity?

Adenosine receptor antagonism and phosphodiesterase inhibition, plus catecholamine release.

What electrolyte and glucose changes are typical of acute theophylline overdose?

Hypokalaemia from intracellular potassium shift and hyperglycaemia, often with lactic acidosis.

Which decontamination method enhances theophylline elimination?

Multiple-dose activated charcoal (gut dialysis).

Which anticonvulsant is avoided in theophylline seizures?

Phenytoin; benzodiazepines are first line, followed by barbiturates.

Why can stopping smoking cause theophylline toxicity?

Smoking induces the liver enzymes that clear theophylline; after quitting, clearance drops and levels rise.

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

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

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