Ibuprofen Overdose

Ibuprofen overdose usually causes mild gastrointestinal upset, but large ingestions can cause central nervous system depression, metabolic acidosis, seizures and acute kidney injury. Most patients recover with supportive care.

It is a common over-the-counter drug overdose. Serious toxicity is unusual under 100 mg/kg and is more likely above 400 mg/kg; large adult ingestions of more than 400 mg/kg cause coma and acidosis. Children and young adults are most often involved.

Risk factors for harm. Dehydration, renal impairment, heart failure, older age, concurrent diuretics or angiotensin converting enzyme inhibitors, and mixed overdose.

Course. Symptoms appear within 4 hours and settle within 24 hours; acute kidney injury may appear at 24 to 72 hours.

Pathophysiology.

Non-selective inhibition of cyclo oxygenase reduces prostaglandin mediated renal perfusion and gastric mucosal protection.

At very high doses, the acid load and mitochondrial effects cause anion gap metabolic acidosis, hypotension and coma.

• Nausea, vomiting, epigastric pain, haematemesis, diarrhoea and tinnitus.
• Headache, dizziness, drowsiness, nystagmus, blurred vision; coma and seizures with large doses.
• Hypotension, bradycardia or tachycardia, apnoea in children and metabolic acidosis in severe poisoning.
• Oliguria, rising creatinine and hyperkalaemia.

Red flags.

• Coma, seizures or respiratory depression.
• Anion gap metabolic acidosis.
• Oliguria or rising creatinine, or gastrointestinal bleeding.

• History of dose in mg/kg, formulation (modified release) and time; co-ingestants including paracetamol.
• Urea, creatinine, electrolytes, venous gas with lactate, glucose, full blood count and liver function if severe; paracetamol and salicylate levels.
• ECG in significant ingestions; ibuprofen level is not useful.
• Urine output and renal function over 24 to 72 hours.

Differential diagnosis. Salicylate poisoning, other NSAID overdose, toxic alcohol ingestion, diabetic ketoacidosis, sepsis and other causes of anion gap acidosis.

• Under 100 mg/kg: no treatment, and discharge after a few hours if asymptomatic.
• Activated charcoal 50 g orally once (1 g/kg, maximum 50 g, in children) if more than 100 mg/kg within 1 hour and the airway is protected. Monitor the airway for aspiration. Avoid with reduced consciousness, ileus or gastrointestinal obstruction; no renal or hepatic adjustment; acceptable in pregnancy.
• Intravenous fluids (0.9% sodium chloride) to maintain urine output over 1 mL/kg/hour and correct dehydration; avoid fluid overload in heart or renal failure.
• Seizures: lorazepam 0.1 mg/kg intravenously (maximum 4 mg for each dose) over 2 minutes, repeated once after 5 to 10 minutes if seizures continue. Maximum 8 mg in total. Monitor breathing, oxygen saturation, blood pressure and sedation. Use lower doses in older adults, respiratory disease and hepatic impairment; no renal adjustment; use only when needed in pregnancy.
• Gastrointestinal protection if bleeding or high risk: omeprazole 40 mg intravenously or orally once daily (twice daily for active bleeding). Maximum 80 mg daily. Monitor haemoglobin and stool or vomit blood. Reduce dose to 20 mg in severe hepatic impairment; no renal adjustment; avoid with clopidogrel.
• Acute kidney injury: fluids, avoidance of nephrotoxins (NSAIDs, aminoglycosides, contrast), treatment of hyperkalaemia, and renal replacement therapy only for refractory acidosis, hyperkalaemia or overload.
• Observe for 4 hours (modified release 6 to 12 hours); discharge when asymptomatic and biochemistry is normal.
• Psychiatric assessment in intentional ingestion.

Monitoring. Urine output and creatinine at 24 hours and 72 hours after significant ingestion; gas and electrolytes until acidosis resolves.

Referral and escalation. Poisons information centre for large ingestions; intensive care for coma, seizures or refractory acidosis; nephrology for kidney injury.

Special groups. Children: calculate dose by weight. Older adults and those on diuretics: higher risk of kidney injury.