Section: Overview
Zinc toxicity is a fairly uncommon disorder that is caused by the ingestion of zinc-containing foreign bodies and is most commonly seen in young dogs. Zinc is directly irritating to the stomach lining so it may cause gastrointestinal irritation.
The most common causes of zinc toxicity include ingestion of:
Pennies minted after 1982. Pennies minted after 1982 have a significantly higher concentration of zinc than pennies minted in 1982 or before. If the copper coating of the penny is broken, the toxicity is increased since the gastric acid can reach the zinc center of the penny causing a rapid absorption of the zinc.
Zinc nuts and bolts, which can be found in transport cages
Galvanized metals
Zinc-containing ointments (e.g. zinc oxide ointment)
Zinc game pieces from board games
What to Watch For
Vomiting
Diarrhea
Lack of appetite
Lethargy
Pale gums
With continued exposure a potentially fatal blood disorder may arise. Zinc interferes with copper and iron utilization in the production of red blood cells. This can lead to a hemolytic anemia in which the red blood cells are destroyed by the body itself since they are abnormal. You will probably notice a pale and often jaundiced (yellow) color to the gums and skin and a brownish, orange color to the urine. High levels of zinc may also cause acute kidney failure.
A toxic dose for a typical dog may be as few as 1 to 3 pennies (50 to 100 mg/kg).
Diagnosis
Diagnostic tests might include the following:
A complete blood count (CBC). Since this test evaluates the red and white blood cells, it is the best diagnostic test to see if hemolytic anemia is present.
A serum biochemical profile. This test monitors for jaundice (elevated bilirubin) and kidney function.
A urinalysis to fully assess kidney function
Abdominal radiographs to visualize zinc-containing foreign bodies
Serum zinc level. Toxic levels of blood zinc are greater than 0.7 mcg/ml.
Treatment
Treatment of zinc toxicity is aimed at removing the initiating cause and providing supportive care.
Zinc-containing items should be removed from the gastrointestinal tract. If the items are in the stomach, endoscopy (a small flexible fiber optic scope) can be used to retrieve the object. If endoscopy is not available, or if the object is further down the gastrointestinal tract, surgery may be required.
Monitor closely for anemia and treat with supportive care if needed. Intravenous fluids or blood transfusion might be needed.
Chelation therapy will decrease toxic zinc blood levels (calcium EDTA or penicillamine).
Gastric irritation may be treated with gastrointestinal protectors.
Home Care and Prevention
Optimal treatment requires a combination of home and professional veterinary care. Administer all prescribed medications, such as penicillamine, as directed by your veterinarian. If there was significant vomiting or diarrhea, you may need to give your pet a bland diet to help restore normal bowel function.
Follow up appointments may be required to monitor the blood for improvement of anemia. However, you should expect continued improvement at home. If your dog is not improving, you should contact your veterinarian to arrange for a further evaluation.
You can prevent zinc toxicity by prevent exposure to any zinc-containing objects. Put coins safely away in areas inaccessible to animals, and do not encourage or allow animals to chew on their travel cages.
If you think you dog has eaten any zinc containing items, contact your veterinarian. He or she might recommend that vomiting be induced. Prompt treatment may prevent more serious illness in the future.
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