The most efficient parenteral chelating agent for lead is calcium disodium ethylene diaminetetraacetic acid
The most efficient parenteral chelating agent for lead is calcium disodium ethylene diaminetetraacetic acid: Excerpt from Avoiding Common Pediatric Errors
Author:
Mindy Dickerman, MD
What to Do - Gather Appropriate Data,
Interpret the Data
Severe lead toxicity is defined as a venous blood lead level >=70 µg/dL, or
having symptoms of encephalopathy. It is a medical emergency even if the
childisasymptomatic.Parenteralchelatingagentsarethemainstayoftherapy
for these children and can be lifesaving. In 1950, calcium disodium ethylene
diamine tetraacetate (CaNa2EDTA) was found to be clinically useful as a
chelating agent in the treatment of lead poisoning. Similar to dimercaprol,
alsoknownasBritishAnti-LewisiteorBAL,CaNa2EDTAincreasestheurinary excretion of lead through the formation of nonionizing soluble chelate.
CaNa2EDTA has very low bioavailability orally and treatment necessitates
hospitalization and parenteral administration.
The appropriate protocol for administration of CaNa2EDTA is controversial. Its use may cause increased lead concentration in the central
nervous system and subsequent increased intracranial pressure. Therefore, CaNa2EDTA is recommended only after administered of dimercaprol.
CaNa2EDTA can beadministered 4hours after the firstdose of dimercaprol
and once urine output is established. CaNa2EDTA can be administered intravenously or intramuscularly. The intravenous route is usually preferred
because it is less painful than the intramuscular route and it permits continuous chelation. However, the intramuscular route should be used in patients
with acute encephalopathy. In addition to the possible elevation in intracranialpressure,themajorsideeffectsofCaNa2EDTAincludelocalreactionsat
the injection site, fever, hypercalcemia, the excretion of other essential minerals, and renal dysfunction. The renal dysfunction can manifest as rising
blood urea nitrogen, proteinuria, or hematuria. There has been a case report
describing the effectiveness of intraperitoneal CaNa2EDTA therapy in patients with renal failure requiring chelation therapy. The use of disodium
salt alone (Na2EDTA), as opposed to calcium disodium salt (CaNa2EDTA),
is crucial because it may result in severe hypocalcemia and possible
death.
The hepatic and renal function of the patient must be observed during
chelation therapy. This includes regular monitoring of transaminases, electrolytes, blood urea nitrogen, creatinine, and renal analyses. CaNa2EDTA
should be temporarily discontinued if the patient becomes anuric although
dimercaprol should be continued. It is also necessary during treatment to
monitor for arrhythmias by continuous electrocardiogram monitoring and
have frequent neurologic assessments.
These chelating agents are very effective at removing lead from the
blood, soft tissues, and the brain and, therefore, can reverse acute encephalopathy, anemia, and renal insufficiency caused by lead intoxication.
TheeffectofusingdimercaprolandCaNa2EDTAtogetherwerefoundinthe
1960storeducethemortalitysecondarytosevereleadintoxicationfrom66%
to about 2%. In contrast to the effects chelation has on mortality and acute
symptoms, this therapy does not affect the neurologic sequelae of chronic
lead toxicity.
Suggested Readings
Committee on Drugs. Treatment guidelines for lead exposure in children. Pediatrics. 1995;96
(1 Pt 1):155–160.
Dietrich KN, Ware JH, Salganik M, et al. Effect of chelation therapy on the neuropsycho
logical and behavioral development of lead-exposed children after school entry. Pediatrics.
2004;114:19–26.
Markowitz ME, Bijur PE, Ruff H, et al. Effects of calcium disodium versenate (CaNa2EDTA)
chelation on moderate childhood lead poisoning. Pediatrics. 1993;92:265–271.
Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
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