Poisoning and Toxicology

Question 1

Name 6 chelators and their route of administration.

Answer 1

1. Dimercaprol- IM
2. Penicillamine- Oral
3. Succimer- Oral
4. CaNa2EDTA- IM or IV
5. Deferoxamine- Parenteral
6. Hydroxocobalamin

Question 2

What chelators would be used in the treatment of mercury poisoning?

Answer 2

Dimercaprol, Penicillamine and Succimer (esp. Children)

Question 3

What chelators would be used in the treatment of lead poisoning?

Answer 3

Dimercaprol, Penicillamine and CaNa2EDTA

Question 4

What chelators would be used in the treatment of iron intoxication?

Answer 4

Deferoxamine but can cause allergic reactions

Question 5

What chelator would be used in the treatment of cyanide toxicity?

Answer 5

Hydroxocobalamin

Question 6

What is the single most important determinant of poisoning outcomes?

Answer 6

good supportive care, including
cardiopulmonary support and protection of airway
assess electroytes
CNS precautions 
Renal function

Question 7

What four methods can be used to limit absorption of poisons?

Answer 7

1. Emetics- not advised for home care and must be used in the first 15-30 minutes.
2. Gastic lavage- Must be used in first 30 minutes
3. Activated Charcoal- Decreases absorption must use in 10:1 ratio. Can cause back diffusion of IV drugs from blood to stomach (ion-trapping)
4. Osmotic Cathartics- Sorbitol 70% good for enteric coated toxins use only after 60 mins or hydrocarbons. laxative

Question 8

What mechanism could you use to clear a drug with a low volume of distribution?

Answer 8

Hemodialysis/peritoneal dialysis. If the drug has a high molecular weight or low solubility then you can use hemoperfusion

Question 9

Name and describe two ways to increase renal excretion.

Answer 9

1. Forced Dialysis- protects kidneys but is worsens pulmonary function
2. Block kidney absorption through either alkalinizing the urine with NaHCO3 or acidifying the urine with NH4Cl or absorbic acid

Question 10

Name and describe a way to enhance metabolism in order to detoxify a drug.

Answer 10

Example: Acetaminophen. Use N-acetylcistine within the first 12-36 to help drive phase II conjugation into a nontoxic metabolite. N-acetylcistine also binds the toxic metabolite of acetaminophen produced during phase I.N-Acetylcistine can be given orally or through IV

Question 11

Name some predisposing factors that would put a patient at higher risk for overdosing on acetaminophen.

Answer 11

Phase II already saturated
CYP2E1 polymorphic
Alcoholic
Decreased Hepatic glutothione

Question 12

In what way are heavy metals toxic?

Answer 12

When overloaded with heavy metals they will bind to enzymes and inhibit them and they also cause alterations in membrane structure.

Question 13

What are the symptoms of methanol poisoning?

Answer 13

Methanol when metabolized will become formic acid which is incredibly toxic. It causes visual changes, blindness and death if untreated. Symptoms also include metabolic acidosis after 4 hours of ingestion.

Question 14

What are the symptoms of ethylene glycol poisoning?

Answer 14

Ethylene glycol becomes Oxalic acid (toxic metabolite). Oxalic acid binds calcium forming precipitates that desposit in the kidney cause kidney damage and failure.

Question 15

What enzyme is the rate limiting step for methanol and ethylene glycol metabolism?

Answer 15

Alcohol dehydrogenase. it is targeted with fomepizole

Question 16

List the treatments for methanol and ethylene glycol poisoning.

Answer 16

1. Ethanol (competitive inhibitor)
2. Fomepizole
3. hemodialysis (remove methanol and ethylene glycol)
4. Sodium bicarbonate for metabolic acidosis