Toxicant Effects and Toxicokinetics
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Questions and Answers

What distinguishes local effects from systemic effects in toxicology?

  • Local effects occur at the site of first contact, whereas systemic effects affect the entire body. (correct)
  • Local effects occur throughout the body, while systemic effects are confined to one area.
  • Local effects can only occur from ingestion, while systemic effects can occur from inhalation.
  • Local effects are always irreversible, while systemic effects are always reversible.

    • Which of the following is an example of a local effect as described in toxicology?

  • Narcotic effects following the inhalation of solvents.
  • Vaginal cancer risk increase due to maternal exposure to diethylstilbestrol.
  • Injury at the site where caustic chemicals are ingested. (correct)
  • Development of leukemia after benzene exposure.

    • Which statement correctly characterizes systemic effects?

  • They only occur following large doses of toxicants.
  • They are always reversible and do not damage tissues.
  • They impact organs or systems throughout the body after exposure. (correct)
  • They happen at the site of contact and do not spread.

    • What type of exposure typically leads to local effects from caustic substances?

    <p>Ingestion of the substance.</p> Signup and view all the answers

    Which toxic effect is usually characterized as a systemic effect?

    <p>Neurological damage after heavy metal exposure.</p> Signup and view all the answers

    Which of the following is most likely to produce local toxic effects?

    <p>Contact with irritants like bleach on skin.</p> Signup and view all the answers

    What is a characteristic of both local and systemic toxic effects?

    <p>Both types can occur after a single exposure.</p> Signup and view all the answers

    Which type of toxic effect is least likely to involve separate systems of the body?

    <p>Local effects resulting from skin contact.</p> Signup and view all the answers

    What characterizes local effects of toxicants?

    <p>Chemical effects observed at the site of contact</p> Signup and view all the answers

    Which of the following correctly describes systemic effects of a toxicant?

    <p>They require absorption and distribution throughout the body.</p> Signup and view all the answers

    What is a key factor in skin absorption of chemicals?

    <p>Condition of the skin can affect absorption efficacy.</p> Signup and view all the answers

    Which statement about volume of distribution (Vd) is accurate?

    <p>Vd influences predicting peak blood concentration of a chemical.</p> Signup and view all the answers

    Which of the following toxicants can cause local effects at their site of absorption?

    <p>Highly reactive gases causing irritation</p> Signup and view all the answers

    What primarily affects the uptake of chemicals by the lungs?

    <p>Chemical reactivity and particle size</p> Signup and view all the answers

    Which factor does NOT increase skin's permeability for chemical absorption?

    <p>Thickness of the skin barrier</p> Signup and view all the answers

    What can happen if certain drugs are used during pregnancy?

    <p>They can lead to increased risk of kernicterus in the fetus.</p> Signup and view all the answers

    What is meant by local effects in toxicology?

    <p>Effects that are restricted to the site of exposure</p> Signup and view all the answers

    Systemic effects in toxicology are primarily characterized by:

    <p>Effects resulting from the distribution of toxins throughout the body</p> Signup and view all the answers

    An example of a substance that may cause local effects when applied topically is:

    <p>Snake venom applied to a bite wound</p> Signup and view all the answers

    Which of the following is NOT a characteristic of systemic toxicity?

    <p>Targets specific organs only</p> Signup and view all the answers

    Which type of toxicology focuses on the effects of pollutants and their systemic impacts on living organisms?

    <p>Environmental toxicology</p> Signup and view all the answers

    What can be a consequence of a local toxic effect from an industrial chemical in the workplace?

    <p>Immediate burn or irritation at the site of contact</p> Signup and view all the answers

    An example of a condition resulting from systemic toxicity due to drug interactions is:

    <p>Excessive drowsiness from combined sedatives</p> Signup and view all the answers

    The statement 'the dose makes the poison' reflects the concept that:

    <p>All substances can pose toxic risks depending on their dosage</p> Signup and view all the answers

    Study Notes

    Toxicant Effects

    • Chlorine gas reacts with lung tissue causing damage and swelling at the site of contact.
    • Systemic effects require absorption and distribution of a toxicant from its entry point to a distant site.
    • Tetraethyl lead produces effects on skin at the site of absorption and then is transported systemically to produce its effects on the CNS and other organs.

    Toxicokinetic (TK) Processes

    • Absorption :

      • Gastrointestinal Tract (GIT): The uptake of chemicals through the GIT depends on several factors, including:
        • The pH of the chemical
        • The presence of food in the stomach
        • The surface area of the GIT
        • The blood flow to the GIT
      • Skin: The uptake of chemicals through the skin depends on:
        • General condition of the skin (abrasions, cuts, etc)
        • Thickness of the skin (arms thin, palms thick)
        • Application of corrosive acids or alkalis organic solvents & which increase the skin's permeability
      • Lung: The uptake of chemicals through the lung depends on:
        • Particle size : Small particles (< 1μm) go down in the alveoli and can cause e.g.silicosis or asbestosis
        • Gas Reactivity : Very reactive gases (HCl, NH3, SO2) are irritating and block respiration and can therefore not be inhaled in larger quantities. While Chemicals with intermediate reactivity and lipophilicity (phosgene, ozone, isocyanates) can be inhaled and give injuries at all levels in the lungs

    • Distribution :

      • Volume of Distribution (Vd) is defined as the apparent volume into which asubstance is distributed.
      • Vd = dose /plasma concentration
      • The blood concentration of a toxicant depends on its volume of distribution (Vd).
      • Small Vd = High concentration in plasma
      • Large Vd = low concentration in plasma
      • Importance of Vd in Toxicology:
        • Predicting peak blood concentration of the chemical taken
        • Deciding whether to apply systemic toxin elimination techniques

    Distribution

    - If used near term during pregnancy or in neonates, certain drugs increase blood levels of unconjugated bilirubin and increase the risk of kernicterus in the fetus or neonate.
- Sulfonamides enter breast milk.
- The top household products ingested are cleaning agents, cosmetics & personal products.

    Lethal Doses of Compounds

    • Lethal dose for each compound.
      • Ethanol: 700 g
      • Salt: 300 g
      • Acetyl salicylic acid: 100 g
      • DDT: 8g
      • Strycnine: 150 mg
      • Nicotine: 100 mg
      • Arsenic (III) oxide: 100 mg
      • Tetrodotoxin: 10 mg
      • Dimethyl mercury: 0,1 mg
      • 2,3,7,8-tetrachlorodibenzodioxine: 0,1 mg
      • Botulinum toxin: 0,001 mg

    Routes of Toxic Exposure

     - Inhalation
 - Ingestion
 - Dermal Absorption
 - Injection

    Classification of Toxicity

     - **Acute toxicity**:  Single exposure to a substance that causes immediate effects. 
 - **Chronic toxicity**:  Repeated exposures to a substance over a prolonged period, leading to adverse effects.
 - **Subchronic toxicity**:  Repeated exposures to a substance for a duration shorter than chronic exposure.

    Toxicological Concepts

    - **Acute or chronic effects**:
    - **Benzene** - 
        - **acute effect**: narcotic
        - **chronic effect**: leukemia

    Toxicological Effects

    - **Immediate Toxic Effects**:  Occur or develop rapidly after a single administration.
- **Delayed Toxic Effects**: Occur after the lapse of some time. 
 - For example, Carcinogenic effects of chemicals usually have a long latency period, often 20 to 30 years after the initial exposure, before tumors are observed in humans.

    Reversible versus Irreversible Toxic Effects

    • Reversible Toxic Effects: The body can repair the damage caused by the chemical.
    • Irreversible Toxic Effects: The damage caused by the chemical is permanent.
    • For example, most liver injury is reversible because the liver has a high ability to regenerate. CNS injury is largely irreversible because differentiated cells of the CNS cannot divide and be replaced.
    • Carcinogenic and teratogenic effects of chemicals are usually considered irreversible toxic effects.

    Local Versus Systemic effects

    • Local Effects: Occur at the site of first contact between the biological system and the toxicant.
    • Systemic Effects: Occur in a location distant from the site of uptake.

    Scope of Toxicology

    - **Descriptive Toxicology**:  Evaluates the toxicity of chemicals exposed to human beings and the environment as a whole via gathering information from animal experimentation 
- **Mechanistic Toxicology**:  Studies the mechanisms by which chemicals or physical agents exert their toxicity on living organisms
- **Clinical Toxicology**:  Concerned with the diagnosis & management of poisoned patients

    Scope of Toxicology

    - **Environmental Toxicology**:  Focuses on the effects of chemical or physical pollutants in the environment on living organisms. It deals with pollution & industrial hygiene.
- **Genetic Toxicology**:  Assesses the effects of chemical and physical agents on the hereditary material (DNA) of living cells.
- **Forensic Toxicology**:  Identifies the cause of death and determines its circumstances in a postmortem investigation

    Toxicologic Terms

    • Toxin: A naturally produced toxic substance such as snake venom.
    • Toxicant: A human-made toxic substance, such as industrial wastes.
    • Xenobiotic: A chemical that is foreign to the normal physiology of the body. It includes drugs and other chemicals such as pesticides.

    Toxicology Terminology

    • Poison : All substances are poisons; there is none that is not a poison. The right dose differentiates a poison and a remedy."The dose makes the poison.“ Paracelsus (1493-1541)

    Types of Toxic Agents: Source

    • Therapeutic Agents: Drug toxicity can be due to over doses, frequent administrations of therapeutic doses & drug interactions (Digoxin & Paracetamol).
    • Industrial Chemicals: Chemicals may contribute to environmental pollution & they may be a direct hazard in the work place they are used (Heavy metals).

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    Chemistry of Toxicology Lecture 1 PDF

    Description

    This quiz explores the effects of various toxicants, including chlorine gas and tetraethyl lead, on the human body. It also delves into the toxicokinetic processes such as absorption through the gastrointestinal tract and skin. Understand the factors influencing these processes and their implications for health.

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