Organic Herbicides - Dipyridyls And Phenoxy Acids

Question 1

How do animals generally get Phenoxy acid toxicosis?

Answer 1

Spayed forages above recommended concentration

Accidental ingestion concentrates or sprays
Grazing on freshly sprayed pasture/ laws

Question 2

Phenoxy acids alter the metabolism of plants which increases their toxicity by increasing accumulation of what compounds?

Answer 2

Nitrates or cyanide

Question 3

T/F: Animals generally dont get phenoxy acid toxicity because plants sprayed with it are less palatable

Answer 3

False

—> can improve palatability of some poisonous plants

Question 4

What species is most sensitive to phenoxy acid toxicity?

Answer 4

Dogs

Acute oral toxicity 100mg/kg (moderately toxic)

Question 5

Where are phenoxy acids absorbed and distributed?

Answer 5

Absorbed in GI (poorly from skin)

Distributed all over the body incl the liver, kidney, and brain

Question 6

The half life of phenoxy acids is ______ in cattle, but _______ in dogs

Answer 6

Hours; 3-4days

Question 7

Phenoxy acids are weak acids, how can their excretion be enhanced?

Answer 7

Alkalinizaiton of urine (eg sodium bicarb)

Question 8

What is the MOA of phenoxy acids?

Answer 8

Irritation of the GI mucosa
Affect skeletal membranes in dogs
Uncouple oxidative phosphorylation and depress ribonuclease synthesis

Question 9

What are the clinical signs associated with phenoxy acids?

Answer 9

GI and neuromucuscular

Vomiting, diarrhea, ulcer on buccal mucosa, rumen atony and bloat (ruminant)
Depression and muscle weakness
Dog only- weakness of the posterior muscles and ataxia with rigidity of skeletal muscles

Question 10

What are lesion that can be seen with phenoxy acid toxicosis?

Answer 10

Nonspecific

Mainly GI damage and degeneration of the liver and kidney
Rumen stasis with ingested food is characteristic

Question 11

What is the best sample for lab diagnostics if you suspect phenoxy acid toxicity?

Answer 11

Forage 
Water
Kidney
Urine
Liver
Stomach contents and feces

Question 12

What biochem data would you see elevated in phenoxy acid toxicity?

Answer 12

ALP
lactate dehydrogenase (LDH) 
Creatine phospholipase (CPK)

Question 13

What is the treatment for phenoxy acid toxicity?

Answer 13

Detoxification

• wash
• activated charcoal

Supportive

• IV fluids
• antidiarrheals and rumenatories

Question 14

Of the diphydril herbicides, what are the restricted use and general use herbicides

Answer 14

Restricted use - Paraquat

General use- Diquat

Question 15

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

Answer 15

True

Question 16

Dipyridyl herbicides are stable in what conditions

Answer 16

Stable -Neutral and acid

Destroyed - Alkali

Question 17

What is the toxicity of dipyridyl herbicides?

Answer 17

25-75mg/kg in cats, dogs, pig, and sheep (highly-moderately toxic)

Question 18

Toxicity of Paraquat is enhanced by what?

Answer 18

Selenium-vitE deficiency
Depletion of tissue glutathione
Oxygen therapy

Question 19

T/F: diquat and Paraquat are poorly absorbed from the GI system

Answer 19

True

Question 20

Paraquat can be distributed all over the body but achieves high concentrations where?

Answer 20

Lung (x10)

Question 21

Where is Paraquat excreted?

Answer 21

Urine

Unchanged

Question 22

What is the MOA of Paraquat and diquat ?

Answer 22

Reduced by nicotinamide-adenine dinucleotide phosphate (NADPH) to produce singlet oxygen

Singlet oxygen reacts with lipid of cell membrane —> hydroperoxides

Free radicals—>cell membrane damage, cellular degeneration, and necrosis

Question 23

What are the early signs of Paraquat and diquat toxicity?

Answer 23

Vomiting, anorexia, and depression

Ataxia, dyspnea, and seizures

Question 24

What are the delayed signs of paraquat and diquat toxicity?

Answer 24

Respiratory signs include tachypnea, dyspnea, harsh respiratory sounds, cyanosis, and reduced pulmonary compliance

Question 25

The respiratory signs seen in subacute/chronic toxicity in dipyridyl toxicity are due to ???

Answer 25

Progressive pulmonary fibrosis

Question 26

What lesions are seen in dipyridyl toxicity?

Answer 26

Pulmonary congestion edema, congestion, hemorrhage, fibrosis, and failure of the lung to collapse

Lingual ulcers
Liver, kidney, and spleen may be congested and enlarged

Question 27

What are the specimens for chemical analysis in acute and chronic cases of dipyridyl toxicity?

Answer 27

Acute - plant material, stomach content, urine

Chronic - lung

Question 28

What are your DDX for things causing tachypnea, dyspnea, harsh respiratory sounds, cyanosis, and reduced pulmonary compliance?

Answer 28

Dipyridyl toxicity
Pneumonia
Inhalant toxicants - gases, vapors, and dusts

Question 29

How do you treat dipyridyl toxicity?

Answer 29

Detox

• emetic
• activated charcoal
• Bentonite/fullers earth choice
• saline cathartics following the adsorbent

Supportive

• fluid therapy
• hemodyalysis or peritoneal dialysis

Biochemical antagonists

• orgotein
• acetylcystine
• ascorbic acid
• niacin or riboflavin

Question 30

What type of supportive therapy is contraindicated in early dipyridyl toxcity and why?

Answer 30

Oxygen therapy

Can increase lung damage