Dipyridyl Herbicides (Paraquat and Diquat) Flashcards
What is an example of a broad-spectrum desiccant contact herbicide?
Dipyridyl herbicides
What are concentrated forms of dipyridyl herbicides used for?
Dilute forms?
- Agricultural use
- Lawns and gardens
What is the concentration of dipyridyl herbicide used for agricultural use?
0.5 lb/acre
What are 2 potential sources of dipyridyl herbicide toxicity?
- Ingestion of concentrates
- Malicious
Are dipyridyl herbicides stable?
No
T/F: Dipyridyl herbicides are rapidly inactivated by light and soil.
True
What type of an herbicide is paraquat?
Dipyridyl herbicides
Are dipyridyl herbicides soluble in water?
Alcohol?
Hydrocarbon solvents?
- Water: yes
- Alcohol: poorly soluble
- Hydrocarbon solvents: no
In what type of environment are dipyridyl herbicides stable in?
destroyed by?
- Stable: neutral or acid
- Destroyed by: alkali
Which dipyridyl herbicide binds strongly to soil?
Paraquat
Dipyridyl herbicides are caustic to what?
Mucous membranes
Which animals are susceptible to dipyridyl herbicides?
All animals are susceptible especially dogs.
What is the oral LD50 range in cats, dogs, pigs, sheep and humans?
25-75 mg/kg
Toxicity of paraquat is enhanced by what 3 things?
- Selenium/Vitamin E deficiency
- Depletion of tissue glutathione
- Oxygen therapy
Daily oral exposure to what level of paraquat causes chronic toxicity and death in dogs?
170 ppm
How is paraquat absorbed by the GIT?
Poorly absorbed
Where is paraquat distributed in high concentrations?
Lungs
Paraquat is excreted in what amount of time?
How?
- Within 24 hours
- Unchanged in urine
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?
Dipyridyl herbicides
What are 3 clinical signs that can be seen with acute dipyridyl toxicosis?
- Vomiting
- Anorexia
- Depression
What are 3 things an acute high dose of dipyridyl herbicide can cause?
- Ataxia
- Dyspnea
- Seizures
Signs may not be observed until how long after exposure to paraquat?
3 days
Delayed signs can be seen how long after dipyridyl herbicide exposure?
These can include what signs?
- 2-7 days
- Respiratory signs: tachypnea, dyspnea, harsh respiratory sounds, cyanosis, reduced pulmonary compliance
Subacute or chronic toxicosis can be seen how long after exposure to dipyridyl herbicides?
7 days to 3 weeks
What type of clinical signs are seen with subacute or chronic dipyridyl herbicide toxicosis?
Respiratory signs due to progressive pulmonary fibrosis.
Where are lesions mainly found with dipyridyl herbicide toxicity?
What can also be seen?
- Respiratory tract
- Lingual ulcers
Which 3 organs may be congested and enlarged with dipyridyl herbicide toxicity?
- Liver
- Kidney
- Spleen
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?
Dipyridyl herbicide
What type of radiographical changes can be seen with dipyridyl herbicide toxicity?
Mild changes in the lungs
Diagnosis of dipyridyl herbicides can be made with what 4 things?
- History
- Clinical signs
- Lesions
- Laboratory
Dipyridyl herbicide toxicity needs to be differentiated from what 2 things?
- Pneumonias
- Inhalant toxicants such as toxic gases, vapors and dusts
Are there any specific antidotes for dipyridyl herbicide toxicity?
No
What kind of herbicide is diquat?
Dipyridyl herbicide
What is the preferred form of detoxification for dipyridyl herbicides?
Activated Charcoal
What is contraindicated for supportive care with dipyridyl herbicide toxicity due to the possibility that it may increase toxicity?
Oxygen
What can be used to cause diuresis and to support kidney function with dipyridyl herbicide toxicity?
Fluid therapy
What are 4 biochemical antagonists that can be used to treat dipyridyl herbicide toxicity?
- Orgotein (superoxide dismutase)
- Acetylcysteine
- Ascorbic acid
- Niacin or riboflavin
Treatments for dipyridyl herbicide are not likely to be much help unless begun within what amount of time?
24 hours of exposure
What is the prognosis for dipyridyl herbicide toxicity?
Guarded or grave