Toxicology Brief: Too much of a good thing: Zinc toxicosis in dogs - Veterinary Medicine
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Toxicology Brief: Too much of a good thing: Zinc toxicosis in dogs
Excessive amounts of this essential mineral can lead to serious consequences, and the condition can easily be mistaken for immune-mediated hemolytic anemia. Be sure to follow these guidelines to detect and treat zinc toxicosis in your patients.


VETERINARY MEDICINE


TREATMENT

Treatment is largely based on supportive care and the removal of the zinc source. Initial goals are to treat dehydration, shock, and electrolyte abnormalities and to enhance diuresis.2,3 Most patients will require fluid therapy at a rate of at least twice maintenance with a balanced electrolyte solution. If the animal is not producing appropriate amounts of urine, the fluid rate will need to be adjusted.

Foreign body removal

If a zinc-containing foreign object is found in the GI tract, it must be removed once the patient is stable.2,3,15 Removal can be performed by endoscopy if the object is within the stomach. During endoscopy the mucosa can be assessed for irritation and ulcerations caused by zinc. Once the object has passed into the small intestine, a laparotomy will be necessary.

Blood products

Blood products (packed RBCs, whole blood) are often needed to treat the hemolytic anemia.2,3,15 If a patient is anemic, it may benefit from the administration of blood products. Plasma is routinely used to treat coagulopathies and may also be used to treat pancreatitis.28 Plasma contains alpha2-macroglobulin, which is a scavenger protein for activated proteases. Protease activity is inhibited by alpha2-macroglobulin. Also, plasma contains some albumin and coagulation factors, thus reducing the potential for DIC, and provides oncotic support in a patient with severe pancreatitis.28 Blood products and plasma also provide colloidal support, which helps maintain blood pressure and, thus, organ perfusion.

Other therapeutic interventions

It is important to initiate treatment with proton-pump inhibitors, such as omeprazole, or H2 blockers to reduce gastric acid production since it will decrease systemic absorption of zinc salts from the GI tract.2,3,15 Gastroprotectants, such as sucralfate, are indicated at normal doses for gastric irritation and ulceration. Antiemetics may be necessary to treat continued nausea from GI ulceration, pancreatitis, and renal failure. Opioids are indicated for pain from pancreatitis.

Chelation therapy

The use of chelation therapy is controversial. With appropriate supportive care, chelation therapy may not be necessary. Chelation will increase the renal excretion of zinc, but it can also increase intestinal absorption.2,3,15 There have been no published studies to document the benefit of chelation therapy.2,3,15

Chelation therapy has been attempted with calcium disodium EDTA, D-penicillamine, and dimercaprol. Calcium EDTA is a heavy metal chelator used for lead or zinc intoxication. It is contraindicated in patients with anuric renal failure. Adverse effects include renal tubular necrosis, vomiting, diarrhea, and depression.2,3,15 The typical doses given are 100 mg/kg divided into four subcutaneous doses per day diluted in 5% dextrose-containing fluids until zinc concentrations normalize.

D-penicillamine is used primarily in dogs for copper storage hepatopathies, but it chelates a variety of heavy metals including copper, lead, iron, mercury, and zinc. Side effects include vomiting, nausea, and depression. The recommended dose is 110 mg/kg/day given orally divided every six to eight hours, 30 minutes before feeding, for one to two weeks.2

CONCLUSION

Attention to patient history should alert you to the potential for exposure to zinc-containing products. Physical and neurologic examinations, laboratory testing, and imaging should also help attain the diagnosis. Complications of zinc toxicosis include the development of pancreatitis, acute renal failure, coagulopathies, and hepatic dysfunction, most of which are reversible with appropriate recognition and care. Many dogs that develop zinc toxicosis can recover quickly if diagnosis and therapy are initiated in a timely manner. It is important to stabilize the patient first and then remove the source of zinc exposure (e.g. removal of metallic object from the GI tract).

Laura Grigsby, DVM, VCA Mission Animal Referral and Emergency Center, 5914 Johnson Drive, Mission, KS 66202.

Emily Medici, DVM, DACVIM, Sugar Land Veterinary Specialists, 1515 Lake Pointe Parkway, Sugar Land, TX 77478.

To view the references for this article, visit http://dvm360.com/ZincToxRefs.


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Source: VETERINARY MEDICINE,
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