Dipyridyl Herbicides (Paraquat and Diquat)

Question 1

What is an example of a broad-spectrum desiccant contact herbicide?

Answer 1

Dipyridyl herbicides

Question 2

What are concentrated forms of dipyridyl herbicides used for?
Dilute forms?

Answer 2

• Agricultural use

- Lawns and gardens

Question 3

What is the concentration of dipyridyl herbicide used for agricultural use?

Answer 3

0.5 lb/acre

Question 4

What are 2 potential sources of dipyridyl herbicide toxicity?

Answer 4

• Ingestion of concentrates

- Malicious

Question 5

Are dipyridyl herbicides stable?

Answer 5

No

Question 6

T/F: Dipyridyl herbicides are rapidly inactivated by light and soil.

Answer 6

True

Question 7

What type of an herbicide is paraquat?

Answer 7

Dipyridyl herbicides

Question 8

Are dipyridyl herbicides soluble in water?
Alcohol?
Hydrocarbon solvents?

Answer 8

• Water: yes
• Alcohol: poorly soluble
• Hydrocarbon solvents: no

Question 9

In what type of environment are dipyridyl herbicides stable in?
destroyed by?

Answer 9

• Stable: neutral or acid

- Destroyed by: alkali

Question 10

Which dipyridyl herbicide binds strongly to soil?

Answer 10

Paraquat

Question 11

Dipyridyl herbicides are caustic to what?

Answer 11

Mucous membranes

Question 12

Which animals are susceptible to dipyridyl herbicides?

Answer 12

All animals are susceptible especially dogs.

Question 13

What is the oral LD50 range in cats, dogs, pigs, sheep and humans?

Answer 13

25-75 mg/kg

Question 14

Toxicity of paraquat is enhanced by what 3 things?

Answer 14

• Selenium/Vitamin E deficiency
• Depletion of tissue glutathione
• Oxygen therapy

Question 15

Daily oral exposure to what level of paraquat causes chronic toxicity and death in dogs?

Answer 15

170 ppm

Question 16

How is paraquat absorbed by the GIT?

Answer 16

Poorly absorbed

Question 17

Where is paraquat distributed in high concentrations?

Answer 17

Lungs

Question 18

Paraquat is excreted in what amount of time?

How?

Answer 18

• Within 24 hours

- Unchanged in urine

Question 19

Which herbicide is reduced by nicotinamide-adenine dinucleotide phosphate (NADPH) to produce singlet oxygen which reacts with lipids of the cell membranes to form hydroperoxides?

Answer 19

Dipyridyl herbicides

Question 20

What are 3 clinical signs that can be seen with acute dipyridyl toxicosis?

Answer 20

• Vomiting
• Anorexia
• Depression

Question 21

What are 3 things an acute high dose of dipyridyl herbicide can cause?

Answer 21

• Ataxia
• Dyspnea
• Seizures

Question 22

Signs may not be observed until how long after exposure to paraquat?

Answer 22

3 days

Question 23

Delayed signs can be seen how long after dipyridyl herbicide exposure?
These can include what signs?

Answer 23

• 2-7 days

- Respiratory signs: tachypnea, dyspnea, harsh respiratory sounds, cyanosis, reduced pulmonary compliance

Question 24

Subacute or chronic toxicosis can be seen how long after exposure to dipyridyl herbicides?

Answer 24

7 days to 3 weeks

Question 25

What type of clinical signs are seen with subacute or chronic dipyridyl herbicide toxicosis?

Answer 25

Respiratory signs due to progressive pulmonary fibrosis.

Question 26

Where are lesions mainly found with dipyridyl herbicide toxicity? What can also be seen?

Answer 26

- Respiratory tract | - Lingual ulcers

Question 27

Which 3 organs may be congested and enlarged with dipyridyl herbicide toxicity?

Answer 27

- Liver - Kidney - Spleen

Question 28

Specimens for chemical analysis can be taken from suspected plant, stomach contents and urine in acute cases or lung in chronic cases of what type of toxicity?

Answer 28

Dipyridyl herbicide

Question 29

What type of radiographical changes can be seen with dipyridyl herbicide toxicity?

Answer 29

Mild changes in the lungs

Question 30

Diagnosis of dipyridyl herbicides can be made with what 4 things?

Answer 30

- History - Clinical signs - Lesions - Laboratory

Question 31

Dipyridyl herbicide toxicity needs to be differentiated from what 2 things?

Answer 31

- Pneumonias | - Inhalant toxicants such as toxic gases, vapors and dusts

Question 32

Are there any specific antidotes for dipyridyl herbicide toxicity?

Answer 32

No

Question 33

What kind of herbicide is diquat?

Answer 33

Dipyridyl herbicide

Question 34

What is the preferred form of detoxification for dipyridyl herbicides?

Answer 34

Activated Charcoal

Question 35

What is contraindicated for supportive care with dipyridyl herbicide toxicity due to the possibility that it may increase toxicity?

Answer 35

Oxygen

Question 36

What can be used to cause diuresis and to support kidney function with dipyridyl herbicide toxicity?

Answer 36

Fluid therapy

Question 37

What are 4 biochemical antagonists that can be used to treat dipyridyl herbicide toxicity?

Answer 37

- Orgotein (superoxide dismutase) - Acetylcysteine - Ascorbic acid - Niacin or riboflavin

Question 38

Treatments for dipyridyl herbicide are not likely to be much help unless begun within what amount of time?

Answer 38

24 hours of exposure

Question 39

What is the prognosis for dipyridyl herbicide toxicity?

Answer 39

Guarded or grave