Organophosphate pesticides
What are the uses for organophosphate pesticides?
- animal and plant insecticides, insecticides synergists, anthelmintics, antiglaucoma, soil nematocides, fungicides, herbicides, rodenticides, and insect repellants
how do you treat organophosphate toxicosis?
- atropine sulfate - repeated every 3-6 hours for a day or morning - 2 PAM chloride - Diphenhydramine to antagonize nicotinic effects - oxygen therapy - supportive therapy
How do you make a diagnosis of organophosphate toxicosis?
- exposure, clinical signs, lesions, laboratory diagnosis and response to specific therapy
What are the clinical signs of acute organophosphate toxicosis?
- inc. salivation, lacrimation, nasal discharge, coughing - inc repiratory sounds from bronchoconstriction and excess bronchial secretions - vomitng, colic, diarrhea, bradycardia, miosis, sweating, and frequent urination
How do animals get organophospate poisoning?
- they are widely used - contaminated feed or drinking water - empty pesticide container used for feeding or watering animals - dusting or spraying animals or animal premises - overdosing
What species are susceptible to organophosphate toxicosis?
All
What OP's must be desulfurated before activated?
Bromophos, diazinon, fenthion, parathion
What affect do organophosphates have on plants?
Can penetrate the waxy coatings of leaves and fruits
What is storage activation?
Chemical alteration due to extended period of storage (1-2 years) causing the chemical to become more toxic than it originally was.
How long do organophosphates last in the environment?
Degrade relatively quickly in the environment persisting about 2-4 weeks (some last longer)
What does DUMBBELLS mean?
Diarrhea, Urination, Miosis, Bradycardia, Bronchospasm, emesis, Lacrimation, Lethargy, Salivation and Seizures
What OP's have direct AchE activity?
Dichlorvos, monocrotophos, trichlorfon
Why are technical grades of organophosphates more toxic than pure compounds?
Due to heat isomerization and impurities
What is the mechanism of action of organophosphate?
Irreversible inhibition of cholinesterases-causing an initial CNS stimulation, CNS overstimulation and ending in a CNS depression. Death is ultimately caused by respiratory depression and failure.
Where are organophosphates absorbed?
Lipophilic-readily absorbed from GIT, skin, MM, or by inhalation
What is the first stage of MoA for OP toxicosis?
Muscarinic receptor stimulation
What is the last stage of MoA for OP toxicosis?
Nicotinic blockade- ganglionic and neuromuscular blockade and CNS depression
What is the second stage of MoA for OP toxicosis?
Nicotinic receptor stimulation-ganglioic and neuromuscular stimulation and CNS stimulation
What medications should be avoided with OPs toxicosis?
Phenothiazines, aminoglycosides, muscle relaxants, Respiratory depressants (Opioids)
What does SLUDGE mean?
Salivation, Lacrimation, Urination, Diarrhea, GIT distress, and Emesis
Parathion, malathion, diazinon, and coumaphos are all OPs that undergo what chemical change that makes them more toxic?
Storage activation
What OP's compound are more toxic in young animals?
Those NOT requiring desulfuration for activation
What OP's compound are less toxic in young animals?
Those requiring desulfuration activation (lethal synthesis) Bromophos, diazinon, fenthion, parathion
What are some common organophosphate pesticides?
chlorpyrifos, coumaphos, diazinon, fenthion, malathion, methyl parathion, temephos
What organophosphates are teratogenic in chickens?
diazinon, parathion, dichlorvos
How do organophosphates cause myopathy?
hemorrhage and necrosis of skeletal muscles in acutely poisoned animals due to inc. ACh
What effect do enzyme inducers (phenobarbital) have on organophosphate toxicosis?
increased or decreased toxicity
What can happen to animals that survive acute poisoning?
may suffer a neurotoxic reaction depending on the compound and species - muscle weakness, ataxia that may progress to paralysis - myopathy, weightloss, secondary infections
What are signs of nicotinic stimulation?
muscle fasciculation, tremors, twitching, spasms and stiff gait caused by hypertonicity
What drugs are contraindicated in organophosphate toxicosis?
neuromuscular blockers, muscle relaxants, phenothiazines, aminoglycosides, opioids, and drugs that depress respiration
are there lesions in animals that die quickly?
no
What is the treatment for neurotoxic effects caused by organophosphate toxicosis?
no treatment
What are the Ddx for organophosphate toxicosis?
pyrethrins, pyrethroids, chlorinated hydrocarbons
What is the cause of death in high exposure in organophosphate toxicosis?
respiratory failure
In what animals do you NOT see clonic or clonic-tonic convulsions?
ruminants
where can organophosphates be located for laboratory diagnosis?
stomach and rumen contents, hair, and skin samples
What can continued exposure to organophosphates lead to?
tolerance
How does the duration of organophospates in the environment affect its toxicity?
toxicity dec. the longer it is in the environment
