Toxicology: Pesticides and Rodenticides

Questions and Answers

What is the mechanism of toxicity for organophosphates?

Inhibition of AChE by phosphorylation (correct)

Inhibition of DNA synthesis

Inhibition of protein synthesis

Inhibition of neurotransmitter release

The bond formed by organophosphates with AChE is permanent and cannot be reversed.

False

What symptoms might indicate exposure to organophosphates?

Miosis, muscle fasciculations, anxiety, tachycardia, salivation.

Which of the following is a highly toxic substance?

Thallium Signup and view all the answers

Match the substances with their toxicity classification:

Thallium = Highly toxic α naphthyl-thiourea = Moderately toxic Warfarin = Low toxicity Strychnine = Highly toxic Signup and view all the answers

What is the treatment for warfarin poisoning?

Activated charcoal, oral Vitamin K1, Fresh frozen plasma. Signup and view all the answers

Zinc phosphide is soluble in water.

False Signup and view all the answers

What is the primary symptom of zinc phosphide toxicity?

All of the above Signup and view all the answers

Study Notes

Pesticides and Toxicology Overview

Inhibition of acetylcholinesterase (AChE) occurs through phosphorylation by organophosphates (OPs), leading to an accumulation of acetylcholine (ACh) and resultant toxicity.
The bond between OP and AChE may become irreversible ("aging") if an antidote is not administered within 24-36 hours due to the detachment of a diethyl group from the phosphate.

Clinical Manifestations

Initial ECG findings include sinus tachycardia and heart block (HB).
Clinical symptoms include chest radiograph findings of pulmonary edema and bronchospasm.
Occupational exposure can lead to electrolyte disturbances like hypokalemia and hyperglycemia.
Epidemic outbreaks may arise from contaminated food sources, with a complete blood count (CBC) showing leukocytosis.
Urine analysis might reveal proteinuria and glycosuria.

Physical Examination Findings

Common symptoms include miosis and muscle fasciculations, indicating cholinesterase inhibition.
Characteristic garlic-like odor of breath.
Other signs include anxiety, diaphoresis, vomiting, diarrhea, tachycardia, and salivation.

Stabilization and Decontamination

Initial management involves intubation and suctioning to maintain airway patency.
Administration of 100% oxygen for 1-2 hours, then down to 70%.
Antidotal therapy includes atropine; treatment ceases when pupil dilation is observed and lung conditions become stabilized.
Diazepam is used to manage seizures, while normal saline may address hypotension.

Toxicity Classifications

Highly toxic substances include thallium, strychnine, and arsenic.
Moderately toxic compounds include α-naphthyl thiourea and cholecalciferol (vitamin D3).
Warfarin, an anticoagulant, is classified as low toxicity, affecting vitamin K's synthesis and leading to a decrease in clotting factors II, VII, IX, and X.

Treatment Protocols for Specific Poisons

General treatment for poisonings includes activated charcoal and vitamin K1 administration:
- 5 mg for children and 20 mg for adults, repeated 2-4 times daily.
- Fresh frozen plasma (FFP) and activated factor VII may be indicated as well.

Zinc Phosphide Toxicity

Zinc phosphide is a dark crystalline, water-insoluble powder with a distinctive rotten fish or phosphorus odor.
It converts to phosphine gas, an inhibitor of cytochrome C oxidase, leading to cellular damage and injury to the gastrointestinal tract, liver, kidneys, and lungs upon inhalation.

Clinical Symptoms of Zinc Phosphide Toxicity

Central nervous system effects: headache, ataxia, seizures, and coma.
Gastrointestinal disturbances: nausea and black vomitus with a rotten fish odor of breath.
Hepatic effects: centrilobular necrosis and jaundice.
Musculoskeletal symptoms encompass paresthesia and intention tremors.
Metabolic issues may include acidosis, hypocalcemia, and tetany.
Cardiovascular complications can lead to shock and dysrhythmias; ocular symptoms may include diplopia.

Supportive Management for Zinc Phosphide

Treatment is predominantly supportive and symptomatic.
Dilution methods using water, milk, or sodium bicarbonate (NaHCO3) are employed as needed.

Description

This quiz covers the critical aspects of toxicology related to pesticides, including rodenticides, pyrethrins, and the mechanism of action of organophosphates. Learn about cholinesterase inhibition, toxicity mechanisms, and the importance of timely antidote administration. Test your knowledge on the effects and implications of pesticide toxicity.