Fundamentals of Toxicology, Poisoning, and Chelation

These flashcards cover key definitions, classifications, mechanisms, clinical features, and treatments related to toxicology, including herbicides, insecticides, heavy metals, antidotes, chelating agents, and principles of poisoning management.

What does the field of toxicology study?

The study of poisons and their effects.

Who is a toxicologist?

A person who studies poisons.

In toxicology terminology, how is a hazard defined?

The likelihood an event will occur based on a product’s packaging, formulation, or accessibility.

How is risk defined in toxicology?

The probability that an event will occur based on patient vulnerability.

What is the difference between a toxic substance and a poison?

There is no difference—both terms denote substances that can cause harm.

What are the three major types of antidotes?

Chemical, mechanical, and physiologic antidotes.

Give an example of a chemical antidote and its mechanism.

Chelators such as EDTA that react with heavy metals to form harmless complexes.

Which mechanical antidote is commonly used to prevent absorption of poisons?

Activated charcoal.

Which physiologic antidote is used for organophosphate poisoning?

Atropine.

What ingredients make up the traditional 'universal antidote'?

Two parts activated charcoal, one part magnesium oxide, and one part tannic acid.

Occupational toxicology in the United States is primarily regulated under what act?

The Occupational Safety and Health Act (OSHA) of 1970.

Which federal agency oversees environmental toxicology issues in the U.S.?

The Environmental Protection Agency (EPA).

What is the primary danger of acute dermal exposure to herbicides?

It is usually limited unless the herbicide is not removed quickly, allowing absorption.

Which herbicide is relatively nontoxic but can cause neurotoxicity and muscle weakness if ingested?

2,4-dichlorophenoxyacetic acid (2,4-D).

What supportive therapy can enhance excretion of 2,4-D in serious poisoning?

Alkaline diuresis or haemodialysis.

Which herbicide causes bloody vomiting followed by pulmonary edema and multi-organ damage when ingested?

Paraquat.

What is the first-line treatment for paraquat ingestion?

Administration of activated charcoal and gut decontamination.

Name one serious complication of diquat poisoning.

Acute renal failure (others include GI ulceration and hypovolemic shock).

Which herbicide marketed as Roundup is most widely used globally?

Glyphosate.

What is a key treatment option when glyphosate poisoning leads to renal failure?

Haemodialysis.

What is the mechanism of organophosphate insecticides?

Inhibition of acetylcholinesterase leading to excess acetylcholine and neurotoxicity.

Which two drugs form the standard antidotal therapy for organophosphate poisoning?

Atropine and pralidoxime.

Why is pralidoxime generally not used in carbamate poisoning?

Because acetylcholinesterase reactivates spontaneously after carbamate exposure.

What ion channel do organochlorine insecticides keep open, causing continuous nerve firing?

Sodium channels.

Which pesticide class includes naturally occurring pyrethrins and synthetic pyrethroids?

Pesticides derived from Chrysanthemum cinerariifolium.

List two common symptoms of pyrethrin or pyrethroid toxicity.

Skin/eye irritation and CNS excitation with possible convulsions.

What naturally occurring pesticide has relatively low human toxicity but can irritate the skin, eyes, and GI tract?

Rotenone.

State four desirable properties of an ideal chelating agent.

High metal affinity, water solubility, tissue penetration, and low inherent toxicity (others include resistance to metabolism and easy excretion).

On what three factors does the effectiveness of a chelator depend?

Affinity for the metal, distribution to where the metal is stored, and ability to mobilize the metal for excretion.

Which chelating agent is oily, has a strong odor, and is effective for acute arsenic and mercury poisoning?

Dimercaprol (BAL).

Name two cardiovascular adverse effects associated with dimercaprol.

Hypertension and tachycardia.

Which oral chelator is preferred for elevated blood lead levels in children?

Succimer (DMSA).

What is the main adverse effect that may require discontinuation of succimer?

Skin rashes.

Which chelator is administered IV to treat lead poisoning and has potential nephrotoxicity?

EDTA (Edetate calcium disodium).

What heavy-metal disorder is penicillamine primarily used to treat?

Wilson’s disease (hepato-lenticular degeneration) due to copper overload.

Which chelator is derived from Streptomyces pilosus and is used for acute iron poisoning?

Deferoxamine.

Name one serious pulmonary complication associated with prolonged deferoxamine infusion.

Acute respiratory distress syndrome (ARDS).

Which orally active tridentate chelator is approved for chronic iron overload in transfusion-dependent patients?

Deferasirox.

What two radioactive or toxic elements does Prussian blue effectively chelate in the gut?

Radioactive cesium-137 and thallium.

Why are children more susceptible to lead poisoning than adults?

They absorb a higher proportion of ingested lead through the GI tract.

List three common chronic symptoms of lead intoxication.

Anemia, skeletal muscle weakness, and lead palsy (wrist/foot drop).

Which chelators are commonly used in management of chronic lead toxicity?

Succimer or EDTA.

What distinctive odor on the breath is associated with acute arsenic exposure?

A garlic-like odor.

Which dermatologic finding—white transverse nail bands—is characteristic of chronic arsenic poisoning?

Mee’s lines.

What is the preferred biological sample for diagnosing acute arsenic exposure?

Urine, with levels >200 µg/L considered abnormal.

Elemental mercury vapor is primarily absorbed through which route?

Inhalation (about 80% is absorbed through the lungs).

Name two hallmark neurological symptoms of organic (methyl) mercury poisoning.

Ataxia and visual disturbances (others include hearing loss and tremors).

Which natural substances are sometimes promoted as mild chelators for heavy metals?

Chlorella, garlic, and cilantro.

What is the first priority (the ABC’s) in initial management of any poisoned patient?

Airway, Breathing, and Circulation.

Which gut decontamination technique involves giving a plant-derived emetic that contains emetine and cephaline?

Administration of Syrup of Ipecac.

Name two contraindications for giving Syrup of Ipecac.

Ingestion of corrosives or when the patient lacks an intact airway reflex (others: low viscosity hydrocarbons, seizures, coma).

Which adsorbent is the cornerstone of gut decontamination for many poisons?

Activated charcoal.

Why are cathartics such as sorbitol used in poisoning management?

To promote bowel evacuation and hasten removal of the toxin-charcoal complex.