Pharmacology Chapter 56-58: Toxicology of Heavy Metals

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Questions and Answers

What is a characteristic symptom of chronic lead toxicity in children?

Basophilic stippling

Severe colicky abdominal pain

Gingival lead lines

Neurocognitive deficits (correct)

What is the primary route of absorption of inorganic lead?

Through ingestion of contaminated food or drink

Through inhalation of industrial fumes (correct)

Through injection of lead-based paint

Through the skin

What is the name of the toxic syndrome due to chronic lead poisoning?

Chelatorism

Erethism

Plumbism (correct)

Toxicology

What is the name of the syndrome resulting from mercury poisoning?

Erethism Signup and view all the answers

What is a sign of acute lead toxicity?

Basophilic stippling Signup and view all the answers

What is a symptom of lead colic?

Severe colicky abdominal pain Signup and view all the answers

What is a result of saturnine gout?

Alteration of uric acid excretion Signup and view all the answers

What is a sign of chronic lead toxicity?

Gingival lead lines Signup and view all the answers

What is a characteristic of chronic lead toxicity?

All of the above Signup and view all the answers

Who is at risk of developing chronic lead toxicity?

Any child with growth retardation Signup and view all the answers

What is the first manifestation of DDT toxicity in humans?

Tremor Signup and view all the answers

Which of the following is NOT a symptom of organophosphorus pesticide toxicity?

Hemolysis Signup and view all the answers

What is the result of phosphorylation of Neuropathy Target Esterase (NTE) in organophosphorus pesticide toxicity?

Progressive chronic axonal neurotoxicity Signup and view all the answers

What is the effect of organochlorine pesticides on the Na+ channel in excitable membranes?

Inhibition of inactivation Signup and view all the answers

What is the association between maternal organochlorine levels and birth defects?

Cryptorchidism and hypospadias in newborns Signup and view all the answers

What is the effect of organophosphorus pesticides on Ca2+ ion transport?

Inhibition Signup and view all the answers

What is the characteristic of organophosphorus pesticide-induced polyneuropathy?

Burning and tingling sensations in the feet, followed by motor weakness Signup and view all the answers

What is the condition associated with triorthocresyl phosphate (TOCP) exposure?

Progressive chronic axonal neurotoxicity Signup and view all the answers

What is the effect of organochlorine pesticides on the CNS?

Stimulation Signup and view all the answers

What is the association between organochlorine pesticide exposure and cancer?

Increased risk of testicular cancer and non-Hodgkin's lymphoma Signup and view all the answers

What is a common effect of PCBs on the fetus?

Deficits in childhood intellectual function Signup and view all the answers

What is a common skin problem associated with PCB exposure?

Chloracne Signup and view all the answers

What is a possible effect of paraquat poisoning on the lungs?

Pulmonary fibrosis Signup and view all the answers

What is a characteristic of PCDDs?

Highly lipophilic and poorly metabolized Signup and view all the answers

What is a possible effect of PCDD exposure?

Increased risk of chronic diseases Signup and view all the answers

What is a common symptom of glyphosate poisoning?

Mild to moderate esophageal erosion Signup and view all the answers

What is a possible effect of PBBs on the environment?

Bioaccumulation Signup and view all the answers

What is a possible treatment for paraquat poisoning?

Activated charcoal Signup and view all the answers

What is a common symptom of paraquat poisoning?

Hematemesis and bloody stools Signup and view all the answers

What is a characteristic of polybrominated biphenyls (PBBs)?

Highly lipophilic and poorly metabolized Signup and view all the answers

Study Notes

Heavy Metals and Chelators

Heavy metals can be toxic to humans and chelators are drugs used to prevent or reverse the toxic effects of heavy metals on enzymes or other cellular targets.
Chelators accelerate the elimination of heavy metals from the body.

Inorganic Lead

Poorly absorbed through the skin.
Acute toxicity results from industrial inhalation of large quantities of lead oxide fumes or ingestion of a large oral dose of lead.
Chronic toxicity signs and symptoms include:
- Anorexia, fatigue, and malaise.
- Neurologic complaints, including headache, difficulty in concentrating, and irritability or depressed mood.
- Weakness, arthralgias, or myalgias.
- Gastrointestinal symptoms.
- Renal interstitial fibrosis and nephrosclerosis.
- Saturnine gout, which is an alteration of uric acid excretion by the kidney, resulting in recurrent bouts of gouty arthritis.
- Gingival lead lines, which are caused by lead sulfide at the gingival margin.

Mercury Poisoning

Erethism is a syndrome resulting from mercury poisoning, characterized by insomnia, memory loss, excitability, and delirium.
Plumbism is a range of toxic syndromes due to chronic lead poisoning, which may vary as a function of blood or tissue levels and patient age.

Pesticides

Organochlorine Pesticides

Classified into four groups: DDT (chlorophenothane) and its analogs, benzene hexachlorides, cyclodienes, and toxaphenes.
They are aryl, carbocyclic, or heterocyclic compounds containing chlorine substituents.
The individual compounds differ widely in their biotransformation and capacity for storage in tissues; toxicity and storage are not always correlated.
They have largely been abandoned because they cause severe environmental damage.
They are now known to be endocrine disruptors in animals and humans.

DDT

DDT in solution is poorly absorbed through the skin.
Has very restricted use for domestic mosquito elimination in malaria-infested areas of Africa.
Tremor may be the first manifestation, continuing to convulsions.

Cyclodienes

Dieldrin absorption from the skin is very efficient.
Interfere with inactivation of the Na+ channel in excitable membranes, causing rapid repetitive firing in most neurons.
Ca2+ ion transport is inhibited, and the major effect is CNS stimulation.

Human Toxicity of Organochlorine Pesticides

Interfere with inactivation of the Na+ channel in excitable membranes, causing rapid repetitive firing in most neurons.
Ca2+ ion transport is inhibited, and the major effect is CNS stimulation.
There is no specific treatment for the acute intoxicated state, and management is symptomatic.
Recent studies suggest that the risk of testicular cancer and non-Hodgkin's lymphoma is increased in persons with elevated organochlorine levels.

Environmental Toxicology of Organochlorine Pesticides

Organochlorine pesticides are considered persistent chemicals.
Degradation is quite slow when compared with other pesticides.
Bioaccumulation, particularly in aquatic ecosystems, is well-documented.

Organophosphorus Pesticides

Based on compounds such as soman, sarin, and tabun, which were developed for use as war gases.
They are absorbed by the skin as well as by the respiratory and GI tracts.
Biotransformation is rapid, as compared to chlorinated hydrocarbon pesticides.

Human Toxicology of Organophosphorus Pesticides

Inhibition of acetylcholinesterase through phosphorylation of the esteratic site.
The signs and symptoms that characterize acute intoxication are due to inhibition of this enzyme and accumulation of acetylcholine.
Some of the agents also possess direct cholinergic activity.
Altered neurologic and cognitive functions, as well as psychological symptoms of variable duration, have been associated with exposure to these pesticides.

Neuropathy Target Esterase (NTE)

Phosphorylation of this enzyme results in progressive demyelination of the longest nerves.
Associated with paralysis and axonal degeneration, this lesion is sometimes called organophosphorus ester-induced delayed polyneuropathy (OPIDP).

Environmental Toxicology of Organophosphorus Pesticides

Organophosphorus pesticides are not considered to be persistent pesticides.
They are relatively unstable and break down in the environment as a result of hydrolysis and photolysis.

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Description

Learn about the human toxicity of heavy metals, including lead, and the role of chelators in pharmacology. This chapter covers the effects of inorganic lead on the human body.