Page 1133 - Cote clinical veterinary advisor dogs and cats 4th

Iron Toxicosis 565

Etiology and Pathophysiology treatment is aimed at providing comprehensive PROGNOSIS & OUTCOME
Mechanism of toxicosis: supportive care and management of hepatic • Varies, depending on how quickly treatment
VetBooks.ir • Causes free radical formation, which leads to Acute General Treatment is started, severity of signs, amount ingested, Diseases and Disorders
injury.
• Direct corrosive damage to GI mucosa
lipid peroxidation and cell membrane injury.
and availability of chelator
○ All tissues are susceptible, but GI tract,
• Guarded to poor if shock and liver damage
• Emesis induction (p. 1188), if exposure was
liver, and heart have the most contact with Decontamination of the patient (p. 1087): • Excellent if only GI signs develop
free iron. within 2 hours and patient is not vomiting occur
spontaneously. With large ingestions of
DIAGNOSIS multivitamins, emesis can be induced up PEARLS & CONSIDERATIONS
to 6-8 hours after exposure because these
Diagnostic Overview tablets dissolve slowly. Comments
The combination of a history of exposure and • Gastric lavage (p. 1117) if a large number • Iron can vary in degree of solubility. Some
consistent clinical signs is highly suggestive of of tablets was ingested and not recovered forms, such as iron oxide (rust), present
iron toxicosis. Serum iron levels and serum iron- in vomitus; however, tablets may form a almost no risk because they are not absorbed.
binding capacity are confirmatory. In patients pharmacobezoar or adhere to gastric mucosa. • Iron can be present in many forms. It is
already showing clinical signs, treatment of • Activated charcoal is not indicated because necessary to convert to elemental iron to
shock is instituted with only a presumptive it binds poorly to iron. determine the dose ingested. Elemental
diagnosis because aggravation of signs can occur • Magnesium hydroxide 5-30 mL/DOG PO iron content = iron form × percentage of
while awaiting confirmation. q 12h for 2-3 days may help reduce iron elemental iron
absorption; efficacy is questionable. ○ Example: if a 20-kg dog ingests one
Differential Diagnosis Stabilization: 325-mg tablet of ferrous sulfate (20%
Depends on stage of intoxication • Intravenous fluids as needed elemental iron), elemental iron content
• Other intoxications that cause similar signs • Gastric protectants = 325 mg × 0.2 = 65 mg elemental iron.
(GI and hepatotoxicosis): sago palm, caustics/ ○ Sucralfate 0.5-1 g PO q 8h, and For this dog, 65 mg/20 kg = 3.25 mg/kg
corrosives, arsenic, copper, microcystin, ○ Famotidine 0.5-1 mg/kg PO, SQ, IM, or elemental iron ingestion.
xylitol, acetaminophen, mushrooms, phenols IV q 12-24h, or • In dogs, < 20 mg/kg elemental iron produces
• GI diseases that cause shock: infectious ○ Omeprazole 0.5-1 mg/kg PO q 24h mild, self-limited GI signs, 20-60 mg/kg can
enteritis, hemorrhagic gastroenteritis, gastric • Antiemetics if needed (e.g., maropitant 1 cause mild to moderate GI signs that may
dilation/volvulus, pancreatitis, GI obstruc- mg/kg SQ q 24h) or ondansetron 0.1-1 mg/ require treatment, and > 60-80 mg/kg may
tion, GI ulcer, peritonitis, and others kg PO q 12-24h or 0.2-0.5 mg/kg IV, IM, cause severe signs and hepatic/renal injury.
• Hepatopathies: neoplasia, leptospirosis, or SQ
idiopathic chronic hepatitis Chelation: Technician Tips
• Deferoxamine (Desferal) is a specific iron • Initial GI signs may worsen rapidly and can
Initial Database chelator: 15 mg/kg/h continuous IV infusion quickly lead to dehydration or shock; fluid
• CBC and serum biochemical profile to rule (or 40 mg/kg IM q 4-8h for 24-72 hours) status needs to be monitored closely.
out other problems and assess liver function, until serum iron levels fall below 300 mcg/ • Deferoxamine can cause hypotension if given
coagulation, dehydration, acid/base status, dL. It can cause hypotension. Most effective too rapidly or if used in a patient in shock;
and renal function within 24 hours of exposure and turns urine monitor blood pressure closely.
• Radiographs may show iron source in GI a pink-brown color (vin rose) while iron is • Dogs ingesting iron-containing formulations
tract, but not all forms are radiopaque. being removed can show black tarry stool color due to
excreted iron oxides (not GI bleeding).
Advanced or Confirmatory Testing Chronic Treatment
• Serum iron If needed: nonspecific support for liver dysfunc-
○ <300 mcg/dL usually does not justify tion (e.g., S-adenosylmethionine 20 mg/kg PO Percentage of Elemental Iron in
chelation but may require treatment of q 24h for 1-3 months; give on empty stomach) Various Iron Salts
GI signs (pp. 442 and 452).
○ >400 mcg/dL along with clinical signs is Compound % Elemental Iron
significant and requires chelator treatment Drug Interactions
• Some human hospital laboratories can Vitamin C can increase GI absorption of Ferric ammonium citrate 15
measure serum iron and total serum iron- iron during toxicosis. Conversely, after iron Ferric chloride 34
binding capacity (TIBC). Usually, serial is out of the GI tract, vitamin C can enhance Ferric EDTA 13
samples are required at 2-4, 12, and 24 chelation with deferoxamine and promote renal Ferric hydroxide 63
hours after exposure. excretion.
○ TIBC may indicate more free iron is Ferric phosphate 37
available, which is toxic. Possible Complications Ferric pyrophosphate 30
• Iron profile (p. 1355). • Acute liver injury, liver failure Ferroglycine sulfate 16
• Hypotension-induced kidney injury
TREATMENT Ferrous fumarate 33
Recommended Monitoring Ferrous carbonate 48
Treatment Overview • Hepatic function should be monitored for Ferrous gluconate 12
Initially, the goal is to decontaminate the patient at least 96 hours after exposure in patients Ferrous lactate 24
if asymptomatic (first stage) or to stabilize the with overt clinical signs.
patient if hypovolemia is present (second-fourth • If abdominal radiographs revealed evidence Ferrous sulfate 37
stages). The next priority is diagnostic testing of the ingested iron source initially, follow-up (anhydrous)
to determine if chelation is needed and to radiographs after emesis or gastric lavage can Ferrous sulfate (hydrate) 20
start chelation if indicated. If the animal is in help identify whether the iron-containing Peptonized iron 17
the third stage (shock and acute liver injury), tablets have been removed.

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