NAC Dosing for Yellow Phosphorus Rodenticide Poisoning
For adult patients with yellow phosphorus rodenticide poisoning, administer N-acetylcysteine (NAC) using standard acetaminophen overdose protocols: oral loading dose of 140 mg/kg followed by 70 mg/kg every 4 hours for 17 doses, or IV loading dose of 150 mg/kg over 15 minutes, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours. 1
Rationale for NAC Use in Yellow Phosphorus Poisoning
While NAC is traditionally the specific antidote for acetaminophen toxicity, emerging evidence supports its use in yellow phosphorus rodenticide poisoning despite the absence of acetaminophen co-ingestion:
Yellow phosphorus is a potent hepatotoxin that causes fulminant hepatic failure as the primary cause of death, with mortality rates of 9-11% in case series 2, 3
NAC demonstrates significant survival benefits in yellow phosphorus poisoning through mechanisms beyond acetaminophen detoxification, likely by replenishing glutathione stores and providing antioxidant effects 3, 4
Meta-analysis of randomized controlled trials shows NAC significantly improves recovery (OR: 3.97; 95% CI: 1.69-9.30) and reduces mortality (OR: 0.25; 95% CI: 0.11-0.59) compared to non-NAC treatment 4
Specific Dosing Protocols
Oral NAC Regimen
- Loading dose: 140 mg/kg orally 1
- Maintenance: 70 mg/kg every 4 hours for 17 additional doses 1
- Mean oral loading dose used in clinical practice: approximately 7,580 mg 3
- Mean maintenance dose: approximately 3,695 mg 3
Intravenous NAC Regimen
- Loading dose: 150 mg/kg IV over 15 minutes 1
- Second dose: 50 mg/kg IV over 4 hours 1
- Third dose: 100 mg/kg IV over 16 hours 1
Weight-Based Considerations
- Use actual body weight for dosing calculations, even in patients weighing >100 kg 5
- Do not cap the dose at a maximum weight cutoff 5
- NAC-related adverse events in heavier patients are relatively common but not serious 5
Critical Timing Factors
- Initiate NAC as early as possible after exposure, ideally within the first 24 hours 3
- Time lag ≥24 hours is a significant risk factor for mortality (RR: 3.48; 95% CI: 1.14-10.65) 3
- Gastric decontamination within 2 hours of exposure significantly improves survival (97.87% vs 84.62%) 2
Clinical Presentation and Monitoring
Yellow phosphorus poisoning has a characteristic delayed presentation:
- Conspicuous absence of symptoms in first 24 hours in most patients 2
- Toxidrome manifests after 24-36 hours (range 18-72 hours) in 72.73% of cases 2
- Dominant manifestations include abdominal pain (52.5%), jaundice (22.2%), coagulopathy (15.2%), encephalopathy (10.1%), and multi-organ failure (17.2%) 2
Poor Prognostic Indicators
- Jaundice at presentation 2
- Hepatic encephalopathy 2
- AST/ALT elevation >1000 IU/L 2
- Metabolic acidosis 2
- Refractory shock 2
Safety Profile
- NAC demonstrates a good safety profile with 93.4% of patients experiencing no adverse effects 3
- Survival rate is significantly higher (p ≤ 0.03) in NAC-treated groups compared to non-NAC groups 3
- NAC also significantly reduces need for intubation/ventilation (OR: 0.25; 95% CI: 0.11-0.60) 4
Additional Management Considerations
- Contact regional poison control center immediately for specific guidance on the particular rodenticide formulation involved 1
- Consider therapeutic plasma exchange as a bridge to liver transplantation in severe cases with progressive hepatotoxicity 6
- Monitor liver function tests (AST, ALT, bilirubin) and coagulation profile (PT, aPTT, INR) serially 2, 6
Common Pitfall
Do not withhold NAC simply because there is no acetaminophen co-ingestion—the evidence supports NAC use specifically for yellow phosphorus poisoning based on its hepatoprotective mechanisms and demonstrated mortality reduction in this population 3, 4.