Zinc toxicity

Background

• Transition metal
• Essential nutrient
• Exposure from diet, medicinal uses, nutritional supplements, and occupational exposures
  • Multiple case reports of zinc toxicity related to ingestion of United States pennies which contain 97.5% zinc

Toxicokinetics

• Absorbed primarily in the jejunum
• Excreted via the GI tract with minimal amounts excreted in the urine
• Accumulates in erythrocytes
  • Whole blood concentrations are 6-7x higher than in the serum
• Inverse relationship with copper
  • Excess zinc absorption will cause a counterregulatory response resulting in copper elimination

Clinical Features

Acute

• GI distress
  • Nausea
  • Vomiting
  • Abdominal pain
  • GI bleeding
  • Partial and full thickness burns causing strictures with zinc chloride solutions with >20% zinc
• Inhalation
  • Lacrimation
  • Rhinitis
  • Dyspnea
  • Acute lung injury
  • Acute Respiratory Distress Syndrome
  • Metal fume fever

Chronic

• Zinc induced copper deficiency
  • Reversible sideroblastic anemia
  • Reversible myelodysplastic syndrome
• Progressive myeloneuropathy
  • Spastic gait
  • Sensory ataxia

Differential Diagnosis

Heavy metal toxicity

• Aluminum toxicity
• Antimony toxicity
• Arsenic toxicity
• Barium toxicity
• Bismuth toxicity
• Cadmium toxicity
• Chromium toxicity
• Cobalt toxicity
• Copper toxicity
• Gold toxicity
• Iron toxicity
• Lead toxicity
• Lithium toxicity
• Manganese toxicity
• Mercury toxicity
• Nickel toxicity
• Phosphorus toxicity
• Platinum toxicity
• Selenium toxicity
• Silver toxicity
• Thallium toxicity
• Tin toxicity
• Zinc toxicity

Evaluation

• BMP
• CBC
• Copper level
• Ceruloplasmin level
• Abdominal films to assess for foreign bodies
• MRI
  • Will show increase T₂ signal in the dorsal columns of the cervical cord

Management

• Oral toxicity
  • Supportive Care
    • Hydration
    • H₂ receptor antagonists or PPI
    • Antiemetics
  • Consider whole bowel irrigation
• Inhalation
  • Supportive care
    • Oxygen therapy
    • Bronchodilators
  • Metal fume fever
    • Usually self limiting
    • CXR usually normal
• Chelation
  • Limited data on use, and data present is based off of case reports and treatment for lead toxicity
  • Consider in patients with hemodynamic compromise
  • CaNa₂EDTA, British antilewisite, DTPA were all successfully used in case reports
  • 1000mg/m²/d IV CaNa₂EDTA every 6 hours
    • Based on a successful case report, but should be given in conjunction with toxicology or poison control center
• Dermal Exposures
  • Do not use water in metallic zinc exposures
    • Concern metal will ignite
  • Remove zinc with forceps and apply mineral oil to affected skin
• Copper replacement
  • Oral copper alone shown to improve hematopoietic effects and prevent further neurological deterioration

Disposition

• Consult Toxicology or poison control