Organic Herbicides - Dipyridyls And Phenoxy Acids Flashcards
How do animals generally get Phenoxy acid toxicosis?
Spayed forages above recommended concentration
Accidental ingestion concentrates or sprays
Grazing on freshly sprayed pasture/ laws
Phenoxy acids alter the metabolism of plants which increases their toxicity by increasing accumulation of what compounds?
Nitrates or cyanide
T/F: Animals generally dont get phenoxy acid toxicity because plants sprayed with it are less palatable
False
—> can improve palatability of some poisonous plants
What species is most sensitive to phenoxy acid toxicity?
Dogs
Acute oral toxicity 100mg/kg (moderately toxic)
Where are phenoxy acids absorbed and distributed?
Absorbed in GI (poorly from skin)
Distributed all over the body incl the liver, kidney, and brain
The half life of phenoxy acids is ______ in cattle, but _______ in dogs
Hours; 3-4days
Phenoxy acids are weak acids, how can their excretion be enhanced?
Alkalinizaiton of urine (eg sodium bicarb)
What is the MOA of phenoxy acids?
Irritation of the GI mucosa
Affect skeletal membranes in dogs
Uncouple oxidative phosphorylation and depress ribonuclease synthesis
What are the clinical signs associated with phenoxy acids?
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
What are lesion that can be seen with phenoxy acid toxicosis?
Nonspecific
Mainly GI damage and degeneration of the liver and kidney
Rumen stasis with ingested food is characteristic
What is the best sample for lab diagnostics if you suspect phenoxy acid toxicity?
Forage Water Kidney Urine Liver Stomach contents and feces
What biochem data would you see elevated in phenoxy acid toxicity?
ALP lactate dehydrogenase (LDH) Creatine phospholipase (CPK)
What is the treatment for phenoxy acid toxicity?
Detoxification
- wash
- activated charcoal
Supportive
- IV fluids
- antidiarrheals and rumenatories
Of the diphydril herbicides, what are the restricted use and general use herbicides
Restricted use - Paraquat
General use- Diquat
T/F: dipyridyl herbicides are rapidly inactivated by light and soil
True
Dipyridyl herbicides are stable in what conditions
Stable -Neutral and acid
Destroyed - Alkali
What is the toxicity of dipyridyl herbicides?
25-75mg/kg in cats, dogs, pig, and sheep (highly-moderately toxic)
Toxicity of Paraquat is enhanced by what?
Selenium-vitE deficiency
Depletion of tissue glutathione
Oxygen therapy
T/F: diquat and Paraquat are poorly absorbed from the GI system
True
Paraquat can be distributed all over the body but achieves high concentrations where?
Lung (x10)
Where is Paraquat excreted?
Urine
Unchanged
What is the MOA of Paraquat and diquat ?
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
What are the early signs of Paraquat and diquat toxicity?
Vomiting, anorexia, and depression
Ataxia, dyspnea, and seizures
What are the delayed signs of paraquat and diquat toxicity?
Respiratory signs include tachypnea, dyspnea, harsh respiratory sounds, cyanosis, and reduced pulmonary compliance
The respiratory signs seen in subacute/chronic toxicity in dipyridyl toxicity are due to ???
Progressive pulmonary fibrosis
What lesions are seen in dipyridyl toxicity?
Pulmonary congestion edema, congestion, hemorrhage, fibrosis, and failure of the lung to collapse
Lingual ulcers
Liver, kidney, and spleen may be congested and enlarged
What are the specimens for chemical analysis in acute and chronic cases of dipyridyl toxicity?
Acute - plant material, stomach content, urine
Chronic - lung
What are your DDX for things causing tachypnea, dyspnea, harsh respiratory sounds, cyanosis, and reduced pulmonary compliance?
Dipyridyl toxicity
Pneumonia
Inhalant toxicants - gases, vapors, and dusts
How do you treat dipyridyl toxicity?
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
What type of supportive therapy is contraindicated in early dipyridyl toxcity and why?
Oxygen therapy
Can increase lung damage
