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How to manage paraquat poisoining

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paraquat poisoning clinical management guideline decontamination hemoperfusion WHO

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paraquat poisoning treatment

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https://pubmed.ncbi.nlm.nih.gov/21615775/

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Paraquat poisoning is a life-threatening emergency. If this may involve a real exposure, call emergency services and a poison center immediately, and take the product container with the patient. Do not wait for symptoms.

Immediate priorities in hospital

  1. Resuscitate and assess airway, breathing, circulation
    • Secure the airway if needed, manage shock, give IV fluids, correct electrolytes and acid-base problems.
    • Avoid giving supplemental oxygen unless there is significant hypoxemia. High oxygen concentrations can worsen paraquat-related oxidative lung injury. Give the lowest concentration needed if oxygen is essential.
  2. External decontamination
    • Remove contaminated clothing.
    • Wash exposed skin thoroughly with mild soap/detergent and water, avoiding skin abrasion.
    • Irrigate eyes copiously with water or normal saline if exposed.
  3. GI decontamination after ingestion
    • If early after ingestion and airway is protected, urgently administer an adsorbent that binds paraquat:
      • activated charcoal, or
      • Fuller’s earth, where available.
    • Do not induce vomiting.
    • Do not perform gastric lavage, because paraquat causes corrosive upper-GI injury and lavage can worsen injury or cause perforation/aspiration.
  4. Urgent toxicology/ICU consultation
    • Contact a regional poison center or medical toxicologist.
    • Admit all significant exposures, including initially well patients. Severe ingestion requires ICU care.

Investigations and monitoring

  • Document product concentration, amount, route, and time of exposure.
  • Serial: ECG, blood pressure, pulse oximetry, arterial/venous blood gas, lactate, renal function, electrolytes, liver tests, CBC, urinalysis, and chest radiograph.
  • Obtain urine dithionite testing and, if available, a plasma paraquat concentration as early as possible. These help estimate prognosis but should never delay treatment.
  • Monitor for oral/esophageal burns. Seek gastroenterology input regarding endoscopy when appropriate.
  • Follow renal function, pulmonary imaging/function, and blood gases for delayed acute kidney injury and progressive lung fibrosis.

Extracorporeal removal

  • Charcoal hemoperfusion, if locally available, is generally considered as early as possible, ideally within a few hours of ingestion.
  • Evidence for survival benefit is uncertain and time-dependent. Hemodialysis or continuous renal replacement therapy is mainly used for kidney failure, severe acidosis, hyperkalemia, or fluid problems, rather than as a reliable way to reverse paraquat toxicity.

Drugs

  • There is no proven antidote.
  • Treatments such as corticosteroids plus cyclophosphamide, N-acetylcysteine, and other antioxidant or immunosuppressive regimens have been used in specialist centers, but evidence is limited or conflicting. They should be directed by a medical toxicologist, not started as a home treatment.
  • Treat pain, vomiting, corrosive injury, renal failure, shock, and respiratory failure supportively.
  • In a severe exposure with poor prognostic markers, early discussions about prognosis and palliative symptom control may be appropriate.

Key complications

  • Early: painful mouth/throat ulcers, vomiting/diarrhea, hypotension, metabolic acidosis, acute kidney and liver injury.
  • Delayed: severe pneumonitis and progressive pulmonary fibrosis, often causing respiratory failure days to weeks later.
Tintinalli emphasizes urgent adsorbent decontamination, no gastric lavage, careful oxygen use, and at least 12 hours of observation even after apparently minor exposure. Tintinalli's Emergency Medicine, 9781260019933, pp. 1347-1348. A review in the British Journal of Clinical Pharmacology likewise concludes that charcoal or Fuller’s earth is routine, lavage should not be performed, and no therapy has reliably changed the high mortality.
A recent systematic review found prognostic value for serum amylase but does not establish a new effective treatment approach (PMID 41766261).

NAC dose in PCM poisoning

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acetylcysteine prescribing information acetaminophen overdose 21 hour IV regimen 150 50 100 mg kg FDA

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acetaminophen poisoning acetylcysteine

For paracetamol (PCM, acetaminophen) poisoning, N-acetylcysteine (NAC) should be started promptly when indicated. Do not delay it if ingestion was >8 hours ago, the amount is unclear, or liver injury is suspected.

IV NAC: standard 3-bag regimen

Total: 300 mg/kg over 21 hours
PhaseNAC doseInfusion time
1150 mg/kg IVover 1 hour
250 mg/kg IVover 4 hours
3100 mg/kg IVover 16 hours
For a 60 kg adult: 9 g, then 3 g, then 6 g.

Alternative IV 2-bag regimen

Used in some toxicology protocols to reduce infusion reactions:
  • 200 mg/kg IV over 4 hours
  • then 100 mg/kg IV over 16 hours
Total remains 300 mg/kg over 20 hours. Follow the protocol used by your hospital/poison center.

Oral NAC regimen

If IV NAC is unavailable or unsuitable:
  • Loading: 140 mg/kg orally
  • then 70 mg/kg orally every 4 hours for 17 doses
Total duration: 72 hours.

When to continue beyond the standard IV course

At the end of the 20-21 hour protocol, continue NAC if any of the following are present:
  • Paracetamol level still detectable
  • ALT/AST rising or abnormal
  • INR elevated
  • Acidosis, renal impairment, encephalopathy, or other evidence of liver failure
A common continuation regimen is 100 mg/kg IV over 16 hours, repeated with serial labs until paracetamol is undetectable and liver tests are clearly improving. This must be supervised by a toxicologist/hepatologist.

Practical cautions

  • Adjust infusion volume, not the mg/kg dose, in small children, fluid-restricted patients, or heart/renal failure.
  • Watch for IV NAC anaphylactoid reactions: flushing, urticaria, wheeze, hypotension. Pause or slow the infusion and treat clinically, then usually restart when stable.
  • Give antiemetics if vomiting affects oral treatment.
  • Use the paracetamol nomogram only for a single acute ingestion with a known time. It is not valid for repeated supratherapeutic ingestion or unknown time of ingestion.
The FDA labeled IV regimen is 150 mg/kg, then 50 mg/kg, then 100 mg/kg, total 300 mg/kg (FDA prescribing information). Recent evidence suggests 2-bag and 3-bag IV regimens have comparable effectiveness, with fewer infusion-related adverse events reported in some two-bag protocols (2025 systematic review).

NAC dose in PCM poisoning

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NAC for paracetamol (PCM) poisoning

Standard IV regimen: total 300 mg/kg

  • 150 mg/kg IV over 1 hour
  • then 50 mg/kg IV over 4 hours
  • then 100 mg/kg IV over 16 hours
Total: 300 mg/kg over 21 hours

Oral regimen

  • 140 mg/kg once
  • then 70 mg/kg every 4 hours for 17 doses
Continue IV NAC beyond 21 hours if paracetamol remains detectable, transaminases/INR are abnormal or rising, or there is liver failure. This should be managed with toxicology/poison-center input.
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