Paracetamol Overdose: Symptoms, Tests, Treatment Guide
Understanding symptoms, risks, diagnosis, and life-saving treatments for paracetamol overdose to prevent liver failure.
Paracetamol, also known as acetaminophen, is a widely used painkiller and fever reducer available in tablets, caplets, soluble forms, and liquids. While safe at recommended doses, overdose is the most common cause of acute liver failure in many countries and can be fatal within days if not treated promptly.
What happens when you overdose on paracetamol?
Normally, the body metabolizes paracetamol through the liver, producing a toxic byproduct called NAPQI, which is neutralized by glutathione—a natural antioxidant. In overdose, glutathione stores deplete rapidly, allowing NAPQI to accumulate and cause severe liver cell damage. This process can overwhelm the liver, leading to failure, and may also affect kidneys, brain, and other organs.
Overdose can occur accidentally from exceeding the maximum daily dose (typically 4g for adults) or intentionally. Factors like chronic alcohol use, malnutrition, or concurrent medications increase risk, as they reduce glutathione reserves. Symptoms may not appear immediately, masking the danger and delaying treatment.
What are the symptoms of paracetamol overdose?
Paracetamol overdose progresses in stages, with many patients asymptomatic initially, which is why immediate medical evaluation is critical even if feeling well.
Stage 1 (0-24 hours)
- Nausea and vomiting (may start a few hours post-ingestion)
- Pale skin or sweating
- Loss of appetite
- General malaise, but often minimal symptoms
Patients may feel fine, leading to delayed help-seeking.
Stage 2 (24-72 hours)
- Right upper abdominal pain (under ribs, liver area)
- Increased nausea/vomiting
- Liver function abnormalities on blood tests
Stage 3 (72-96 hours)
- Jaundice (yellowing of skin/eyes)
- Confusion, drowsiness (hepatic encephalopathy)
- Bleeding tendencies due to clotting issues
- Worsening liver failure
Stage 4 (4-5 days or later)
- Recovery or multi-organ failure (liver, kidneys, brain)
- Coma, seizures, or death without transplant
Other complications include kidney failure (reduced urine output), hypoglycemia, lactic acidosis (rapid breathing), and pancreatitis. Family may notice empty packets or notes; bring these to hospital.
Understanding your overdose
Healthcare teams assess based on amount ingested, timing, body weight, alcohol use, and intent. Staggered overdoses (multiple doses over time) are riskier and harder to predict. Blood paracetamol levels are plotted on a nomogram (graph) to determine toxicity risk.
Tests used to diagnose paracetamol overdose
Diagnosis relies on history, exam, and labs. Early exams may be normal.
Paracetamol level
Blood test 4+ hours post-ingestion; levels above treatment line indicate need for antidote.
Liver function tests (LFTs)
Measure ALT/AST (elevated in damage), bilirubin (jaundice), albumin, prothrombin time (clotting).
Renal function tests
Check creatinine/urea for kidney involvement.
Blood sugar levels
Hypoglycemia common in liver failure; monitored hourly.
Arterial blood gas
Detects acidosis (high acid, poor prognosis).
Additional tests: Full blood count, electrolytes, clotting screen, ECG if needed.
How can paracetamol overdose be treated?
Treatment is time-sensitive; start in A&E with stabilization (IV fluids, monitoring). High-risk cases go to ICU. Antidote given if levels high or uncertain timing. Psychiatric evaluation mandatory pre-discharge.
N-acetylcysteine (NAC) treatment
NAC (e.g., Parvolex) replenishes glutathione, detoxifies NAPQI. Most effective <8 hours post-overdose.
- IV regimen: 3 bags over 21-24 hours (150mg/kg over 1h, 50mg/kg over 4h, 100mg/kg over 16h)
- Side effects: Itching, rash, wheeze (manageable by slowing drip/antihistamines)
- Stops if levels safe; continue if ongoing damage
Monitor LFTs/renal function during/after.
Further treatments
- Supportive care: Anti-emetics, glucose for hypoglycemia, vitamin K/fresh frozen plasma for bleeding
- Liver transplant for irreversible failure (assess via King’s College criteria: pH<7.3, INR>6.5, creatinine>300µmol/L, encephalopathy grade 3-4)
| Risk Factor | High-Risk Transfer to Liver Unit |
|---|---|
| INR | >2 at 24h, >3 at 48h, >6 at 72h |
| Creatinine | >200µmol/L |
| Encephalopathy | Grade 3 or 4 |
| Acidosis | pH <7.3 |
Prevention of paracetamol overdose
- Stick to max 4g/day (lower if elderly/liver issues/alcoholics)
- Avoid combining products (e.g., cold remedies with paracetamol)
- Store safely, child-proof caps
- Educate on risks; seek help for pain/fever alternatives
- Alcoholics: Risk multiplies; abstain or dose cautiously
Prognosis
With NAC <8h, excellent (>95% survival). Delayed: 20-30% mortality without transplant. Early presentation key.
Frequently Asked Questions (FAQs)
Q: How much paracetamol is an overdose?
A: >4g in 24h for adults; toxic single dose >150mg/kg. Always consult dosing.
Q: What if I think I overdosed but feel fine?
A: Seek emergency care immediately—symptoms lag behind damage.
Q: Can children overdose?
A: Yes; dose by weight (15mg/kg). Symptoms similar; NAC effective.
Q: Does alcohol worsen it?
A: Yes, induces enzymes, depletes glutathione.
Q: Is NAC safe?
A: Generally yes; minor reactions common, anaphylactoid not true allergy.
Q: When to call 999?
A: Severe pain, jaundice, confusion, no urine >8h, vomiting.
This comprehensive guide emphasizes urgency: Paracetamol overdose is treatable if addressed promptly. Consult professionals for advice.
References
- Paracetamol Overdose: Symptoms and Treatment — Patient.info. 2023. https://patient.info/treatment-medication/paracetamol-overdose
- Paracetamol overdose A&E leaflet — University Hospitals Sussex NHS Foundation Trust. 2023. https://www.uhsussex.nhs.uk/resources/paracetamol-overdose-emergency-department-leaflet/
- Acetaminophen Poisoning — Merck Manuals (Professional Version). 2024-01-13. https://www.merckmanuals.com/home/injuries-and-poisoning/poisoning/acetaminophen-poisoning
- Acetaminophen Toxicity — StatPearls, NCBI Bookshelf (NIH). 2023-07-17. https://www.ncbi.nlm.nih.gov/books/NBK441917/
- Paracetamol Poisoning — Royal Children’s Hospital Melbourne Clinical Guide. 2023. https://www.rch.org.au/clinicalguide/guideline_index/paracetamol_poisoning/
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