22 Questions
What is the treatment for OP intoxication?
Atropine and pralidoxime (2-PAM)
What is the effect of 2-PAM on aged enzyme?
It is not effective in regenerating the enzyme
What is the mechanism of action of pyrethrum and pyrethrins?
Voltage-gated sodium, calcium, and chlorine channels, as well as benzodiazepine receptor
What is the example of a biological insecticide?
Pyrethrum
What is the treatment for convulsions in OP poisoning?
Diazepam (5 to 10 mg, IV)
Why are oximes not effective in antagonizing the toxicity of carbamoyl ester inhibitors?
They even aggravate the toxicity
What is the primary mechanism of action of pyrethroids in insects?
Keeping Na channels open for a long time
Why are pyrethroids relatively non-toxic to animals and humans?
Because of their rapid detoxification and lack of accumulation
What is the primary effect of rotenone on the respiratory system?
Initial respiratory stimulation followed by depression
What is the mode of action of rotenone on nerve conduction?
Blockage of electron transport in mitochondria
What is the primary mode of action of chlorophenoxy compounds in plants?
Mimicry of auxins, leading to uncontrolled growth
What is the combination of 2,4-D and 2,4,5-T commonly known as?
Agent orange
What is the primary effect of paraquat on the lungs?
Formation of reactive oxygen species (ROS)
What is the primary mode of action of bipyridyl derivatives in plants?
Uncoupling of oxidative phosphorylation
What is a major difference between Organophosphate (OP) insecticides and Organochlorine insecticides?
OP insecticides do not bioaccumulate in tissue or organisms
What is the result of the inhibition of AchE by Organophosphate insecticides?
Accumulation of Ach leading to stimulation of cholinergic synapses
What is the treatment for life-threatening OCl insecticide poisoning?
General decontamination and supportive treatment, along with Diazepam or Phenobarbital
What is the reason behind the increasing use of Pyrethrins as pesticides?
Due to the high toxicity of Organophosphate compounds
What is the effect of repetitive stimulation of the CNS in OCl insecticide poisoning?
Interference with respiratory function and resulting acidosis
Which of the following is NOT an Organophosphate insecticide?
Carbaryl
What is the MOA of Organophosphate and Carbamate insecticides?
Inhibition of AchE
What is the result of the phosphorylation of AchE by Organophosphate insecticides?
Formation of a stable, phosphorylated, and largely unreactive enzyme
Study Notes
Insecticides and Herbicides
- Pyrethroids keep Na channels open, causing persistence depolarization
- Pyrethroids have low toxicity in animals and humans due to:
- Little storage or accumulation
- Efficient detoxification
- Differences in Na channels, making them more toxic to insects
Rotenone
- Causes acute poisoning in animals, characterized by:
- Initial respiratory stimulation
- Followed by respiratory depression
- Ataxia and convulsions
- Death by respiratory arrest
- Blocks electron transport in mitochondria by inhibiting oxidation linked to NADH2
- Causes nerve conduction blockade
- Rare cases of human intoxication
Herbicides
- Defined as compounds that can kill or severely injure plants
- Used to eliminate plant growth or kill plant parts
- Examples:
- Chlorophenoxy compounds (2,4-D, 2,4,5-T, and their salts and esters)
- Bipyridyl derivatives (paraquat and diquat)
Chlorophenoxy Compounds
- 2,4-D and 2,4,5-T are used to destroy broadleaf weeds
- Can be used in combination as Agent Orange
- Mimic the action of auxins, hormones that stimulate growth
- Uncouple oxidative phosphorylation and decrease oxygen consumption
- Less effective in non-target organs
Bipyridyl Derivatives
- Paraquat: a non-selective contact herbicide
- Highly toxic to lungs
- Toxicity is due to formation of reactive oxygen species (ROS)
- Diquat: another bipyridyl derivative
Organophosphate (OP) Insecticides
- Chronic effect: delayed neurotoxicity (OPIDN)
- Treatment: atropine and pralidoxime (2-PAM)
- General supportive measures: decontamination, gastric lavage, artificial respiration, and treatment of convulsions with diazepam
Insecticides of Biological Origin
- Pyrethrum: extracts from the chrysanthemum flower
- Pyrethrins: synthetic derivatives of pyrethrin
- Rotenone: extracts from leguminaceae genera
Mechanism of Action
- Voltage-gated sodium, calcium, and chlorine channels are possible targets
- Benzodiazepine receptor (GABA antagonist action) is also a target
This quiz covers the mechanisms of toxicology, specifically in relation to insecticides and the sodium channel. Topics include the effects of pyrethroids and rotenone on animals and humans.
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