Overview

• Toxicity results from the ingestion of zinc-containing material.
• Causes gastrointestinal inflammation and hemolytic anemia; may cause multiple organ failure (e.g., renal, hepatic, pancreatic, and cardiac), DIC, and cardiopulmonary arrest.

Signalment

Most frequently reported in young, small-sized dogs (i.e., <12 kg); can occur in all species of all sizes.

Signs

• Anorexia
• Vomiting
• Diarrhea
• Lethargy
• Pale or icteric mucous membranes
• Hemoglobinemia
• Hemoglobinuria
• Orange-tinged feces
• Tachycardia

Causes & Risk Factors

• There are a variety of zinc compounds with different bioavailabilities: zinc carbonate and zinc gluconate (dietary supplements), zinc chloride (deodorants), zinc pyrithione (shampoos), zinc acetate (throat lozenges), zinc oxide (sunblock, Desitin, calamine lotion), zinc sulfide (paints), metallic zinc (coins).
• Toxic doses have not been well defined.
• Brass: alloy of copper and zinc.
• Toxicities result from ingestion of zinc-containing material: U.S. pennies minted after 1982 (most common source), nuts, bolts, staples, galvanized metal (e.g., nails), pieces from board games, zippers, miscellaneous toys, jewelry.
• Organic forms of zinc (e.g., zinc oxide) generally cause only gastrointestinal inflammation.
• Acidic environment within the stomach promotes rapid leaching of zinc from the ingested substance, allowing for zinc to be absorbed.

Differential Diagnosis

• Numerous causes of gastrointestinal upset: viral, bacterial, parasitic, immune mediated.
• Numerous causes of hemolysis: immune-mediated hemolytic anemia, Babesia, onion and garlic toxicosis, mothball toxicosis (naphthalene), caval syndrome, acetaminophen, coral snake venom, pit viper venom, brown recluse spider venon, mushrooms, overhydration, skunk spray.

CBC/Biochemistry/Urinalysis

• Hemolytic anemia, with possible Heinz body formation.
• Regeneration will occur if there is enough time: high nucleated RBC counts, basophilic stippling, polychromasia, elevated reticulocytes.
• Target cells.
• Spherocytosis-mild and often inconsistent.
• Leukocytosis with a neutrophilia.
• Hemoglobinemia.
• Bilirubinemia.
• High liver enzymes AST, ALP; less common are elevations in GGT and ALT.
• Elevated pancreatic enzymes-amylase and lipase-may indicate multiple organ failure.
• Proteinuria.
• Pigmenturia (hemoglobin, bilirubin).
• Azotemia (high BUN and creatinine)-not common.

Other Laboratory Tests

• Serum zinc levels often exceed 5 ppm (approximate normal range: 0.70–2 ppm for dogs and cats).
• Blood must be collected in non-zinc-contaminated blood tubes.
• Coagulation panel-may indicate DIC (prolonged PT and PTT, hypofibrinogenemia, thrombocytopenia, and high FDPs).
• Frequent monitoring of PCV is indicated because the decline in PCV can be rapid.

Imaging

• Abdominal imaging-may reveal metallic object(s) in the gastrointestinal tract.
• Often the zinc object has passed (via vomit or feces) by the time the patient is admitted.

Diagnostic Procedures

ECG-may reveal arrhythmias and ST-segment abnormalities.

Drug(s)

• Chelation therapy may not be warranted once the source of the excess zinc is removed-zinc levels drop fairly rapidly (over a few to several days) via excretion into bile, pancreatic secretions, and urine.
• CaEDTA-100 mg/kg diluted in 5% dextrose SC, divided into 4 doses per day (treatment as for lead poisoning) if clinical improvement or reduced blood zinc is not accomplished by removal of zinc objects.
• Penicillamine-110 mg/kg/day PO divided 6–8h for 5–14 days (treatment as for lead poisoning)-generally less frequently used than CaEDTA.
• Heparin-150 U/kg SC q6h; for DIC.
• H2-receptor antagonists (e.g., cimetidine, ranitidine, famotidine), proton pump inhibitors (e.g., omeprazole), and antacids used alone or in combination-may help reduce stomach acidity and the rate of release of zinc.
• Antiemetics.

Contraindications/Possible Interactions

Avoid aminoglycoside antibiotics and other potential nephrotoxins-risk of acute renal failure.

Patient Monitoring

• ECG-monitor for evidence of arrhythmias and ST-segment alterations.
• Coagulation profile, PCV, RBC, amylase, lipase, BUN, creatinine, ALP, AST, and ALT-monitor for the first 72 hours after zinc removal.
• Monitor serum zinc levels.

Expected Course and Prognosis

• Multiple organ failure (e.g., kidney, liver), DIC, pancreatic disease, cardiopulmonary arrest-potential outcomes.
• Rapid removal of the source of zinc may provide progressive improvement over 48–72 hours; complete recovery possible.

See Also

Poisoning (Intoxication) Therapy

Abbreviations

• ALP = alkaline phosphatase
• ALT = alanine aminotransferase
• AST = aspartate aminotransferase
• DIC = disseminated intravascular coagulation
• ECG = electrocardiogram
• GGT = gamma-glutamyltransferase
• PCV = packed cell volume
• PT = prothrombin time
• PTT = partial thromboplastin time
• RBC = red blood cells