A West Highland White Terrier named Sierra died last month down the road from me in Denver, CO after eating just one penny. Unfortunately, she arrived at the veterinary clinic in the final throes of zinc toxicosis. They couldn’t save her.
At this point you might be confused, thinking, “What do zinc and pennies have to do with each other?”
In fact, American pennies minted after 1982–and some produced during that year–contain 96% zinc, a much cheaper metal than copper.
Other potential sources of toxic levels of zinc for dogs include:
- Canadian pennies minted after 1996
- galvanized hardware
- plumbing supplies
- old toys, and
- zinc-containing sunblock, diaper ointment, and other lotions (e.g., calamine)
Once swallowed, zinc’s first effect is to irritate the lining of the gastrointestinal tract. It can cause vomiting, diarrhea, and a loss of appetite.
But these are the least of the dog’s concerns.
Zinc is easily absorbed into the bloodstream.
This isn’t too surprising since small amounts of zinc, derived from the diet, are essential for normal body function. Even zinc that might appear to be “locked up” in a copper-coated penny or other metallic objects will eventually be set free and absorbed by the action of strong acids in the stomach.
When zinc levels reach a critical point, they start to adversely affect red blood cells.
We don’t know exactly why, but high levels of zinc cause red blood cells to burst through a process called intravascular hemolysis. Severe intravascular hemolysis is devastating for two reasons:
Anemia and hemoglobinemia can lead to
- destruction of red blood cells leading to anemia and an inability of the blood to carry sufficient amounts of oxygen.
- release of hemoglobin; free, circulating hemoglobin (hemoglobinemia) is toxic to tissues.
- rapid breathing
- pale and/or yellow mucous membranes and skin
- dark urine
- multiple organ failure
- disseminated intravascular coagulation (an oftentimes fatal condition characterized by blood clotting when it shouldn’t and/or failing to clot when it should)
- cardiopulmonary arrest
Small dogs, like Westies, are at highest risk for zinc toxicosis.
As Sierra’s case points out, it doesn’t take much zinc to have disastrous consequences on small bodies.
Also, coins, bolts, etc. are less likely to get stuck in the stomach of large breed dogs. Instead, they will pass out of the gastrointestinal tract before much zinc has been absorbed.
Therapy for zinc toxicosis can be successful so long as it is begun before the zinc caused too much damage.
When the source of zinc is still present, it must be removed either surgically or with an endoscope. If removal has to be delayed while the patient is stabilized, antacids can be prescribed to decrease stomach acidity and reduce the absorption of more zinc. Blood transfusions and chelation therapy (the use of substances that bind to metals and aid in their elimination from the body) is sometimes necessary in severe cases. The dog may also need treatment for organ failure and/or disseminated intravascular coagulation. After the removal of the source, blood zinc levels should return to normal in about two days.
As we all know, some dogs are willing to eat just about anything. Take special care to keep zinc-containing objects out of their reach.
Count Your Change: Penny’s Zinc Poisoning