Inj. NAC dose in paraquat poisoning
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paraquat poisoning "N-acetylcysteine" treatment
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IV N-Acetylcysteine (NAC) in Paraquat Poisoning
Role of NAC
NAC is used as an antioxidant adjunct in paraquat poisoning. Paraquat causes toxicity through redox cycling → superoxide radical generation → lipid peroxidation → pulmonary fibrosis and multi-organ failure. NAC replenishes glutathione stores and scavenges reactive oxygen species.
Important caveat: NAC is not a specific antidote for paraquat. Textbooks classify it among experimental antioxidant treatments (alongside vitamins C & E, deferoxamine, selenium). The evidence for survival benefit is limited, but it has low toxicity and is routinely used.
Dosing
There is no established paraquat-specific NAC protocol in major guidelines. The dosing used clinically is extrapolated from the acetaminophen IV NAC regimen (the standard 21-hour "Rumack-Matthew" protocol):
| Phase | Dose | Duration |
|---|---|---|
| Loading dose | 150 mg/kg IV (max 15 g) | Over 60 minutes |
| First maintenance | 50 mg/kg IV (max 5 g) | Over 4 hours |
| Second maintenance | 100 mg/kg IV (max 10 g) | Over 16 hours |
| Total standard course | 21 hours | — |
Tintinalli's Emergency Medicine (line 192) specifically states: "Acetylcysteine may provide benefit and is of low toxicity. It should be administered continuously while there is evidence of acute toxicity in the inpatient setting." This means the infusion is often continued beyond 21 hours — running continuously for as long as the patient remains acutely toxic and hospitalized, unlike the time-limited course used for acetaminophen overdose.
Key Points for Clinical Use
- Dilution: Use 5% dextrose (D5W) as the diluent (not normal saline for IV NAC).
- Monitoring: Watch for anaphylactoid reactions (flushing, bronchospasm, urticaria) — slow the infusion rate if these occur.
- Oxygen caution: Supplemental O₂ should be withheld unless SpO₂ is critically low, because oxygen enhances the paraquat redox cycle and worsens pulmonary injury.
- Combination therapy: NAC is used alongside:
- Dexamethasone 8 mg IV every 8 hours for the first 72 hours (may continue for weeks if pulmonary progression risk remains)
- Hemoperfusion (if initiated within 4 hours of ingestion)
- Activated charcoal (if within 2 hours of ingestion)
Sources:
- Tintinalli's Emergency Medicine: A Comprehensive Study Guide, Bipyridyl Herbicides section
- Brenner and Rector's The Kidney, Paraquat – Treatment section
- The Harriet Lane Handbook, 23rd ed., Antidote: N-Acetylcysteine
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