Heavy Metal Toxicity Flashcards
What is the mechanism of heavy metal toxicity?
Binds to sulfhydryl groups.
What are some distinctions among Lead, Arsenic, Mercury and Thallium toxicities?
Lead: most common
Arsenic: N/V/D, prolonged QT
Mercury: classic clinical findings
Thallium: very PAINFUL peripheral neuropathy
How do chelating agents work?
They form complexes with heavy metals, preventing them from reacting. Their stable heterocyclic ring makes them easy to excrete.
Why does British Anti-Lewisite (BAL) [dimercaprol] have allergic implications?
It is mixed with peanut oil.
What is dimercaprol used for?
Arsenic, lead and inorganic mercury poisoning (want to use early).
What happens to BAL-metal chelates in acidic urine?
They dissociate, which is why urinary alkalinization is employed during BAL therapy to prevent metal-induced renal toxicity.
What is 2,3-dimercaptosuccinic acid used for?
Mostly lead poisoning. Also arsenic, mercury and cadmium poisoning.
Very well tolerated, mild side-effects.
What is edetate calcium disodium often confused with?
Na2EDTA, which causes severe hypocalcemia.
What toxicity does edetate calcium disodium have?
Renal toxicity.
What is Prussian Blue used for? How does it work?
Thallium and Cesium poisoning.
Since it is not absorbed, it catches these metals in the GI tract. Also, it forms a concentration gradient which forces metals out of the tissue periphery.
What is the toxicologic mechanism behind iron?
Direct corrosive effect to GI mucosa, leading to severe vomiting, eventually leading to volume depletion.
Also causes high anion gap metabolic acidosis and has a direct negative inotropic effect.
What is used to chelate iron? How does it work?
Deferoxamine
It chelates free iron, but not iron in transferrin, hemoglobin, etc.
Excreted in urine, which results in a reddish brown color.
Useful for ACUTE iron poisoning (don’t give after 24 hrs, since it can then cause acute lung injury).
What is the mechanism of 2,3-dimercaptosuccinic acid?
It binds arsenic and mercury to sulfur and lead and cadmium to sulfur/oxygen
What is the mechanism of edetate calcium?
It displaces calcium with lead.
