Treatment of Arsenic Poisoning

Quick Reference Facts

• Fatal Dose: 200-300 mg of arsenic trioxide
• Fatal Period: 1-2 days
• Blood level indicating serious poisoning: >1.5 mg/100 mL
• Normal blood arsenic: <4 mg/L; urine <0.03 mg/L

Treatment

1. Gastric Decontamination

• Emetics - to induce vomiting promptly
• Gastric lavage - the stomach should be emptied and then thoroughly and repeatedly washed via stomach tube with large amounts of warm water and milk
• The stomach should be washed out at intervals to remove iron compounds and adherent arsenic
• Nasogastric suction - should be done as arsenic is re-secreted in the gastrointestinal tract
• Whole bowel irrigation

• Butter and greasy substances prevent absorption (helpful)
• Alkalis should NOT be given - they increase the solubility of arsenic
• Freshly precipitated hydrated ferric oxide and dialyzed iron are NOT recommended

2. Chelation Therapy (Antidotes)

Important exception: Chelation therapy is ineffective in arsine gas poisoning.

3. Supportive Measures

• Demulcents - to lessen irritation of the GI tract
• Castor oil or magnesium sulfate - to prevent intestinal absorption of arsenic (cathartics)
• Glucose-saline with sodium bicarbonate - helpful to combat shock and improve the alkali reserve
• Hemodialysis or exchange transfusion - in cases of renal failure

Summary Approach

1. Decontaminate first - emesis or lavage, repeated gastric washing, whole bowel irrigation
2. Chelate - BAL is the classic agent; DMSA/DMPS are preferred when available
3. Support - IV fluids with sodium bicarbonate for shock, dialysis for renal failure
4. Monitor - urinary arsenic levels guide duration of chelation (target <50 mg/24h)

Treatment of Mercury Poisoning

Quick Reference Facts

• Fatal Dose: 1-2 g of mercuric chloride
• Fatal Period: 3-5 days
• Normal blood mercury: <10 μg/L; Urine <20 μg/L; 24-hour urinary excretion <50 μg/L
• Chronic exposure threshold: Blood >35 μg/L; Urine >150 μg/L

Treatment of Acute Mercury Poisoning

1. Gastric Decontamination

• Gastric lavage using any of the following (to bind the mercury):
  • Milk
  • Egg-white
  • 5% salt-poor albumin
  • 2-5% sodium bicarbonate solution
• Sodium formaldehyde sulfoxylate - NOT recommended
• Activated charcoal - of uncertain benefit
• Cathartics should NOT be given
• Whole bowel irrigation may be beneficial

2. Chelation Therapy

• BAL + penicillamine combination must NOT be used - they may form a toxic compound
• Ca-EDTA must NOT be used - it is nephrotoxic in the presence of mercury

3. Supportive Measures

• Urine must be kept alkaline at all times
• High colonic lavage with 1:1,000 solutions of sulfoxylate twice daily
• Hemodialysis - indicated if there is significant kidney damage

Chronic Mercury Poisoning (Hydrargyrism)

1. Gingivitis, stomatitis, and salivation (with a blue line at the gum-tooth junction)
2. Tremors (Danbury tremors) - begin in hands, progress to lips, tongue, arms, and legs; moderately coarse with jerky movements
3. Neuropsychiatric changes - erethism (mercury madness): extreme timidity, embarrassment, loss of memory, irritability, and in severe cases delirium and hallucinations

Treatment of Lead Poisoning

Quick Reference Facts

• Fatal Dose: ~20 g lead acetate; ~40 g lead carbonate
• Fatal Period: 1-2 days (acute)
• Diagnostic blood level: >20 μg% in blood; >150 μg/L in urine
• Serious poisoning threshold: Blood lead >70 μg/100 mL

Treatment of Acute Lead Poisoning

1. Gastric lavage with 1% solution of sodium or magnesium sulphate
2. Demulcents
3. Combination of BAL + Calcium Disodium Versenate (CaNa2 EDTA) or DMSA
4. Penicillamine
5. Calcium chloride - 5 mg of a 10% solution IV causes deposition of lead in the skeleton from the blood
6. Peritoneal or hemodialysis
7. Symptomatic treatment

Treatment by Blood Lead Level (Chronic / Severity-Based)

(A) Severe Acute Poisoning WITH Encephalopathy

• BAL: 4 mg/kg immediately in children. Repeat every 4 hours until blood lead falls below 40 μg/100 mL, then reduce to 12 mg/kg/day in 3 divided doses
• CaNa2 EDTA: 75 mg/kg/day as IV infusion; reduce to 50 mg/kg/day as condition improves
• Continue until asymptomatic, then shift to oral chelation:
  • D-penicillamine: 10 mg/kg/day, OR
  • DMSA (succimer): 10 mg/kg/dose three times daily for 20 days

(B) Severe Poisoning WITHOUT Encephalopathy (Blood lead >70 μg/100 mL)

1. BAL: 12 mg/kg/day
2. EDTA: 50 mg/kg/day
3. Discontinue BAL when blood lead falls below 40 μg/100 mL, but continue EDTA for 5 more days
4. Continue oral chelation until blood lead falls below 15 μg/100 mL or for 3 months

(C) Moderate Poisoning (Blood lead 45-75 μg/100 mL)

1. EDTA: 50 mg/kg/day
2. Begin oral chelation when blood lead level falls below 40 μg/100 mL

(D) Mild Poisoning (Blood lead 20-35 μg/100 mL)

1. D-penicillamine: 30 mg/kg/day in 3 divided doses
   • Start with one-fourth of the calculated dose
   • Double the dose after 1 week; double again after another week
   • Continue until blood lead <15 μg/100 mL or for 3 months
2. DMSA (succimer): 10 mg/kg/dose three times daily for 20 days - more effective and less toxic than D-penicillamine

Summary Table (Table 27.2 from Reddy)

Detailed Chelator Notes

CaNa2 EDTA (Calcium Disodium Versenate)

• Acts as an ion exchanger - calcium is exchanged for lead, forming a soluble, stable, unionized lead chelate
• Increases urinary excretion of lead fiftyfold above untreated baseline
• Dosage: 5 mL of 20% solution diluted in 250-500 mL normal saline or 5% glucose, given as slow IV drip over 1 hour, twice daily for 5 days, repeatable after 2-day interval

BAL (British Anti-Lewisite / Dimercaprol)

• Dose: 4 mg/kg every 4 hours
• Chelates lead both intracellularly and extracellularly; 2 BAL molecules combine with 1 lead atom
• Excreted primarily via bile - drug of choice in renal impairment
• BAL must be given at least 4 hours before EDTA - EDTA mobilizes lead from tissue stores and can aggravate symptoms

Penicillamine

• Dose: 0.3-0.5 g orally, 1-5 times daily
• Effective for circulating lead but less effective than EDTA
• May be continued for 1-2 months

DMSA (Succimer / Dimercaptosuccinic Acid)

• Superior to EDTA
• Dose: 10 mg/kg/dose three times daily for 20 days, then same dose every 12 hours for 14 days

DMPS (Dimercaptopropane Sulfonic Acid)

• Also an option for chelation

Supportive Measures

1. Thiamine: 10-50 mg/kg - helps improve neurological manifestations
2. Calcium gluconate (IV): useful in relieving lead-induced colic
3. Magnesium or sodium sulphate: converts unabsorbed lead salts into highly insoluble lead sulphate and hastens passage via stool

Bone Lead Mobilization (for lead stored in bones)

• Diet poor in calcium + ammonium chloride (1 g ten times daily) - mobilizes lead deposited in bones into blood for excretion
• High doses of parathormone have similar effects

Prophylaxis (Factory Workers)

1. Maintenance of proper ventilation in factories
2. Maintenance of personal hygiene and periodic medical examination
3. Diet rich in calcium
4. Small amount of sulfuric acid in water
5. Weekly saline purgative