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 (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.
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
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.