Toxicology Heavy Metals

Question 1

A ____ is something that can cause harm, _____ is the chance of it happening

Answer 1

Hazard, Risk

Question 2

Most drugs are eliminated through ____ order kinetics, but at high concentrations saturation is reached and elimination then becomes _____ order

Answer 2

1st

Zero

*Prolong half life when saturated as well as increase unbound free fractions

Question 3

The apparent volume in which a substance is distributed is called volume of Distribution, is a large or small Vd more easily accessed?

Answer 3

Small

*Larger Vds are not good candidates for hemodialysis

Question 4

________ is the accumulation of a toxic agent across time whereas _____ is accumulation through the food chain

Answer 4

Bioaccumulation

Biomagnification

Question 5

Naturally occurring elements with high atomic weight and a density 5-times greater than water are called?

Answer 5

Heavy Metals

Question 6

What are the three most toxic heavy metals?

Answer 6

1-Lead
2-Mercury
3-Arsenic

*based on prevalence and severity

Question 7

Both children and pregnant women absorb more lead because their bodies have a greater demand for what?

Answer 7

Calcium and Iron

*50% ingestion rather than 10-15%

Question 8

Leads half life is 1-2 months and cause what 3 main symptoms?

Answer 8

1-Headaches
2-Neurocognitive deficits
3-Kidney damage

*substitutes for Ca in bone

Question 9

Dark lines on the gingiva are cause by what heavy metal?

Answer 9

Lead

*called Burtonian Lines

Question 10

What are 5 ways lead interferes with the body?

Answer 10

1-Interferes with Ca++ use
2-Causes anemia
3- Immunosuppression
4-Binds sulfhydryl groups on any enzymes and co-factors
5-Crosses BBB and concentrates in gray matter, can cross placenta

Question 11

Treatment for lead toxicity is to remove the exposure which is done principally with which chelator?

Answer 11

• Edetate Calcium disodium (EDTA)
• Followed by Succimer

*can cause rebound intoxication as the bone re-equilibrates

Question 12

Found as a liquid at room temperature what are three main ways we are exposed to mercury?

Answer 12

1-Fish
2-Dental Amalgam
3-Thermometers

Question 13

Mercury is highly reactive with which essential dietary element?

Answer 13

Selenium

*needed to prevent reverse oxidative damage

Question 14

Acute intoxication of mercury can effect the gingiva how?

Answer 14

Gingivostomatitis

Question 15

Chronic mercury intoxication can cause neurological and psychiatric problems historically common to which profession?

Answer 15

Hatter (used mercury in leathers to make hats)

*Mad Hatter’s Disease

Question 16

Mercury toxicity is treated using which two chelators?

Answer 16

1-Dimercaprol (if acute, can cause renal issues)

2-Succimer

Question 17

What are two main exposure sources of Arsenic?

Answer 17

1-Industrial contamination
2-Groundwater contamination

*absorbed through respiratory and GI tracts. Keratinized tissues act as a depot

Question 18

What are 4 consequences of arsenic toxicity?

Answer 18

1-Hyper pigmentation
2-Peripheral neuropathy
3-Carcinogenic in lungs, skin and bladder
4-Hemolytic effect on RBC

*increases ROS

Question 19

Chelators are useful for _____ arsenic intoxication but not for ______

Answer 19

Acute

Chronic (irreversible damage to several vital organs)

*Chelators also ineffective in acute arsine inhalation

Question 20

The longer the half-life of a heavy metal the ______ effective chelation will be

Answer 20

Less

*treat as early as possible

Question 21

Which FDA approved mono therapy chelator is used for Arsenic and Mercury but not lead?

Answer 21

Dimercaprol

*can be used in combination for lead

Question 22

Dimercaprol is not water soluble and has a narrow therapeutic index and has consequently been largely replaced by what two chelators?

Answer 22

Succimer and unithiol

Question 23

Which water soluble derivative of dimercaprol is not FDA approved and increases renal excretion of mercury, arsenic and lead?

Answer 23

Unithiol

*orall or IV

Question 24

Which chelator is a water soluble dimercaprol and is FDA approved for children and adults with lead, arsenic and mercury poisoning?

Answer 24

Succimer

Question 25

Which drug is FDA approved and indicated as the 1st line treatment for chelation of lead but is contraindicated in anuric patients?

Answer 25

EDTA (Edetate Calcium Disodium)

*nephrotoxicity when used 5+ days

Question 26

What are the 4 criteria for biocompatible dental materials?

Answer 26

1-Not harm pulp/soft tissue
2-No toxic diffusible substance
3-Free of sensitizing agents
4-Not carcinogenic

Question 27

The greatest amount of mercury is released during which dental procedure?

Answer 27

Dry polishing of amalgam restorations

Question 28

To prevent pulpitis caused by unpolymerized monomers in resin composite _____ the recommended time of curing exposure and ____ place should be done

Answer 28

twice

Incremental

Question 29

How can zinc phosphate cement exposure be limited?

Answer 29

Proper mix or use of a resin-modified glass ionomer cement

Question 30

Though it is not a heavy metal, how does cyanide poison?

Answer 30

inhibits cytochrome C oxidase

Question 31

What is the antidote for cyanide poisoning?

Answer 31

Hydroxycobalamin