Lecture 9 Pesticide Toxicology

Question 1

What would be expected if paraquat was ingested in large quantities?

Answer 1

Death by multi-organ failure or cardiogenic shock

Within 1-4 days

Question 2

What would be expected if paraquat was ingested in small quantities?

Answer 2

Irreversible lung fibrosis

Death within several weeks

Question 3

What is the mechanism of paraquat?

Answer 3

Paraquat uptake into the alveolar cell. Paraquat is converted to paraquat radical by NADPH, an oxygen radical also forms. Oxygen radical reacts with Fe3+ to form hydrogen peroxide. Which cannot be degraded due to the lack of NADPH.

Question 4

What is the primary route of exposure of paraquat?

Answer 4

Oral ingestion, and then almost completely absorbed in GIT.

-highly polar so does not cross dermal or lung

Question 5

Where is paraquat mostly distributed in the body?

Answer 5

Kidneys, lungs, liver, and muscle - highly oxidative tissue. Taken up by active transport.

Question 6

What form of elimination occurs for paraquat?

Answer 6

Renal elimination - glomerular filtration and tubular secretion. Is excreted in bring almost unchanged.

Question 7

What are the possible treatments for paraquat?

Answer 7

Activated charcoal to reduce absorption
Haemodialysis, forced diuresis to increase elimination. Need to act early otherwise will already have significant amount in lungs, also has short clearance rate so if use late there would be no point
Don’t use gastric lavage because won’t be able to put tube down damaged oesophagus

Question 8

How can we diagnose paraquat poisoning?

Answer 8

Urine colour change test

Paraquat radical will cause blue colour when mixed with sodium dithionite

Question 9

What feature is used as a good prognosis measure of paraquat poisoning?

Answer 9

Creatinine concentration.
Greater portion of survivors have creatinine concentration in normal range
Smaller portion of dead have creatinine concentration in normal range

Also: oropharyngeal burns, respiratory signs

Question 10

How do we determine the sensitivity and specificity of using creatinine as a diagnosis tool?

Answer 10

Sensitivity = #dead that had higher creatinine concentration than threshold / actual dead
Specificity = #survived that had lower creatinine concentration than threshold / actual survived