Zinc Toxicity

Sources: Pennies minted after 1982, zinc oxide ointment such as Desitin, and metallic hardware of transport cages are three most common causes of zinc toxicosis. Also, some paints, sunscreens, metal game pieces, water from galvanized metal containers, and certain fertilizers, nails, and staples.

Mechanism of Action: Zinc is a gastric mucosal irritant and systemic toxicosis depends on the rate of absorption from the GI tract. The acid pH of the stomach is an ideal environment for the gradual release of zinc.  Once leeched from the material ingested, zinc is absorbed and transported to various organs. Exact mechanism of action is not fully understood but it may interfere with certain enzymes and be able to cause direct damage to cell membranes and organelles. Zinc is mainly excreted in the feces, and about 25% in the urine.

Clinical Signs: GI signs are typically the first to appear and include vomiting, diarrhea, and anorexia. Generalized depression is also a possible symptom.

Severe signs are intravascular hemolytic anemia, hemoglobinuria, hematuria, prehepatic jaundice, weakness, and death.

Diagnosis:

  • CBC demonstrating regenerative anemia with hemolysis or hemoglobinuria, increased nRBCs, polychromasia, basophilic stipling, target cells.
  • Increased alkaline phosphatase
  • Hyperbilirubinemia
  • Azotemia
  • Radiographs with evidence of a metallic foreign body
  • Labs can run blood trace metal levels

Treatment: 

  • RBC transfusion
  • IV fluids
  • Monitor urine output
  • FFP if signs of DIC are present
  • Chelation therapy with CaEDTA –Tx may last days to weeks as zinc levels normalize
  • H2 blockers
  • Remove metallic foreign body surgically or endoscopically
  • Treat renal failure if present.

Prognosis:  Guarded and depends on the severity of the anemia and the extent of any liver, renal, or pancreatic insufficiency. Favorable outcome not expected if there is any sign of DIC. Quick recognition and intervention are key to a good outcome.

References: 

Gfeller, Roger W., Handbook of Small Animal Toxicology & Poisoning (St.Louis:Mosby, 1998), pp.264-267

Peterson, Micheal E., Small Animal Toxicology ( Philadelphia: W.B. Saunders Company, 2001), pp. 758-759