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ABBEY MSII U6 > Pharm chelation therapy > Flashcards

Pharm chelation therapy Flashcards

1
Q

what is the mechanism of heavy metal toxicity?

A
  • binds to sulfhydryl groups in various organ systems and enzymatic processes throughout the body
  • affinity for organ system toxicity is a result of the characteristics of the heavy metal and its distribution sites
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2
Q

effects of acute heavy metal exposure on the cardiovascular system

A

tachycardia and in some cases dysrhthmias and cardiomyopathy

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3
Q

effects of acute heavy metal exposure on the CNS

A

altered mental status and peripheral neuropathy

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4
Q

effects of acute heavy metal exposure on the GI system

A

nausea, vomiting and diarrhea

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5
Q

effects of acute heavy metal exposure on the renal system

A

proteinuria, aminoaciduria and acute tubular necrosis

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6
Q

effects of chronic heavy metal exposure

A

more subtle findings - increased effects at organ sites that may be less accessible acutely (esp CNS and PNS, hematologic, renal, skin/skeleton/CT abnormalities, neoplasm)

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7
Q

how is heavy metals diagnosis made?

A
  • routine PE
  • question occupation and hobbies
  • labs: CBC with peripheral smear, renal function, liver function, u/a, acid-base balance and radiograph anaylsis
  • serum metal levels, whole blood metal levels, urine metal levels, hair analysis
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8
Q

what are the 4 most common heavy metal exposures?

A

lead, arsenic, mercury, thallium

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9
Q

what is done for acute toxicity of heavy metal toxicity?

A
  • ABCs
  • GI decontamination (activated charcoal, whole bowel irrigation)
  • chelation therapy
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10
Q

what is done for chronic toxicity of heavy metals?

A
  • removal from source!!

- chelation therapy

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11
Q

how does chelation work? (mechanism)

A

-chelating agent forms complexes with heavy metals and prevents or reverses the binding of metallic cations to reactive groups (ligands)

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12
Q

what are characteristics of ideal chelators?

A
  • VD of the chelator greater than VD of chelate
  • high water solubility
  • ability to reach the site of where the metal is stored
  • capacity to form nontoxic complexes
  • stable at physiologic pH
  • low affinity for trace elements
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13
Q

british anti-lewisite (BAL) class and mechanism

A

dithiol: forms stable chelate via electron pair donation and coordination with metal ion

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14
Q

BAL implication

A

mixed with peanut oil (peanut allergies)

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15
Q

BAL therapeutics

A

arsenic, lead, inorganic mercury poisoning

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16
Q

BAL side effects

A

renal toxicity (unless urine is alkalinized), pain at injection site (IM), nausea, vomiting, increases in BP and HR

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17
Q

what is done to prevent metal-induced renal toxicity? why must this be done?

A

urinary alkalinization because dissociation of BAL-metal chelate in acidic urine happens

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18
Q

2,3-dimercaptosuccin acid (DMSA) class and mechanism

A

dithiol: coordinate bonding to sulfur (arsenic and mercury) or sulfur and oxygen (lead and cadmium)

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19
Q

DMSA therapeutics

A

arsenic, lead, mercury, cadmium poisoning

20
Q

DMSA side effects

A

mild ALT/AST elevation - otherwise well tolerated

21
Q

when is DMSA most used?

A

lead poisoning in children

22
Q

how is DMSA administered

A

orally - can be given outpatient

23
Q

edetate calcium disodium (EDTA) mechanism

A

displacement of calcium by lead

24
Q

EDTA therapeutics

A

lead poisoning

25
Q

which version of EDTA used? which should not be used? why?

A

CaNa2EDTA - NOT Na2EDTA because it causes severe hypocalcemia

26
Q

EDTA side effects

A

malaise, fever - renal toxicity

27
Q

how is EDTA administered? when?

A

IV at hospital - esp given when there is encephalopathy due to lead poisoning

28
Q

prussian blue mechanism

A

stays in gut and not absorbed until it grabs metal - goes into gut and is excreted that way

29
Q

prussian blue therapeutics

A

thallium and radioactive cesium poisoning

30
Q

prussian blue side effects

A

well tolerate - not absorbed after oral dosing into systemic circulation

31
Q

normal role of iron

A

various intracellular processes (accepts and donates electrons), extracellular is bound to transferrin

32
Q

when does iron toxicity occur?

A

free iron in circulation

33
Q

what are the pharmacokinetics of iron?

A

peak serum concentrations occur 2-6 hours after ingestion (overwhelmed transferrin and increase in circulating free iron)

34
Q

local toxicity of iron

A

direct corrosive effect to GI mucosa (leading to hematemesis, melena, periportal necrosis of liver and intetional ulceration and edema)
-resultant volume depletion

35
Q

systemic toxicity of iron

A
  • high anion gap metabolic acidosis
  • uncoupler of oxidative phosphorylation!
  • direct negative inotropic effect
  • hypotension (vasodilator)
36
Q

early clinical effects of iron toxicity

A

local tissue effects of GI tract (nausea and lots of vomiting) within 6 hours

37
Q

intermediate clinical effects of iron toxicity

A

nausea and vomiting may temporarily decrease with an increase in development of metabolic acidosis and sequelae

38
Q

late signs of iron toxicity

A

severe local and system effects - hepatotoxicity, ARDS, renal, gastric outlet obstruction

39
Q

chelator for iron poisoning

A

deferoxamine

40
Q

deferoxamine mechanism

A

chelates FREE iron and iron transported between transferrin and ferritin

41
Q

deferoxamine side effects

A

rate-related hypotension, anaphylactoid reactions, yersinia enterocolitis (facilitates growth of unusual organisms), acute lung injury/ARDS
-can only treat for 24 hours before acute lung injury manifests

42
Q

clinical pearls for lead poisoning in kids

A

colic, lower levels associated with IQ changes, think PICA

43
Q

clinical pearls for lead poisoning in adults

A

hypertension, tolerate higher lead levels

44
Q

clinical pearls for arsenic poisoning

A

rice-water diarrhea, prolonged QT, arsenical dermatitis, “rain drops on a dusty road”

45
Q

clinical pearls for mercury poisoning

A

labile mood “mad as a hatter”, intention tremor, mercury salts: caustic

46
Q

clinical pearls for thallium

A

painful neuropathy, alopecia

ABBEY MSII U6 (18 decks)

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