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BI316 > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

What is a toxin?
name two different toxins

A

It is an agent capable of producing a deleterious response in a biological system.
- Poison and Venom

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2
Q

What is poison?

A
  • A substance capable of producing deleterious biological responses if present in sufficient amounts.
  • Potential enrichment of hydrophobic toxins in the body.
  • Potential conversion of substances into toxic derivatives.
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3
Q

How is poison taken?

A

It is swallowed, inhaled or absorbed through the skin

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4
Q

How is venom taken?

A

It is actively injected into the bloodstream via a bite or sting

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5
Q

What are the classification of harmful effects?

A
  1. Two mechanistic categories of harmful effects:
    (a) effects related to the principal pharmacological action of the drug
    (b) effects unrelated to the pharmacological action
  2. Two different patterns of incidence:
    (a) excessive effect of the drug, which occurs in any subject given a large dose
    (b) aberrant effects unrelated to normal drug action
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6
Q

What is therapeutic index (TI)?

A

The ratio of the dose that produces toxicity/lethality to the dose that produces a clinically desired or effective response in a test population.

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7
Q

Formula for therapeutic index

A

LD50/ED50
LD50 = the lethal dose for 50% of the test population or 50% mortality in test system, i.e. cells in culture
ED50 = effective dose for 50% of the test population
TD50 = the dose of drug that cause a toxic response in 50% of the population

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8
Q

What are examples of narrow TI drugs?

A
  • Digoxin
  • Lithium
  • Gentamicin
  • Warfarin
  • 5-FU (5-fluorouracil)
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9
Q

What does a narrow TI exhibit?

A

Narrow TI drugs exhibit a samll margin of safety between the therapeutic effect of a drug and its toxic effects.

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10
Q

What is digoxin?

A

Used for acute treatment of heart conditions such as atrial fibrillation. It decreases the function of sarcalemmal Na+/K+ ATPase pump of cardiac myocytes.

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11
Q

What is lithium?

A

Used for acute treatment of manic phase in manic depression. Interference with the neuro-transmission process via reduced sensitivity to transmitters in nerves.

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12
Q

What is gentamicin?

A

Used for broad-spectrum antibiotics for the treatment of bacterial infections. It acts by inhibition of bacterial protein synthesis.

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13
Q

What is warfarin?

A

It is an anti-coagulant drug employed in the prevention of thrombosis. It inhibits the synthesis of biologically active forms of Ca2+-dependent clotting factors.

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14
Q

What is 5-FU?

A

It is an anti-metabolite cancer drug. It inhibits thymidylate synthase causing interruption of thymidine synthesis and thus lack of essential nucleosides for DNA replication.

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15
Q

What is toxicology?
What are xenobiotics?

A
  • It is the study of the adverse effects of xenobiotics on living organisms.
  • Xenobiotics are chemicals that are foreign to living organisms.
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16
Q

What are toxicokinetics and toxicodynamics?

A
  • Toxicokinetics is the absorption, distribution, metabolism, storage and excretion of an agent.
  • Toxicodynamics are the effects of the chemical and its metabolism on an organism.
17
Q

What is mechanistic toxicology?

A

It is the identification and analysis of the molecular mechanisms by which xenobiotics exert toxic effects in a biological system.

18
Q

What is target organ toxicity?

A

In sufficient amounts, many xenobiotics trigger an organ-selective pattern of toxicity.

19
Q

What are the major targets of organ-selective toxicity?

A
  • Liver
  • Kidney
  • Respiratory system
  • Nervous system
  • Heart and vascular system
  • Reproductive system
  • Immune system
  • Blood
  • Skin
  • Eye
20
Q

What are target organ toxicity due to?

A
  • Major route/ pathway of exposure
    • Ingestion (GI-tract)
    • Inhalation (lungs)
    • Topical (skin)
    • Intravenous (bloodstream)
  • Pattern of distribution in a biological system
  • Metabolism / Biotransformation
    • Bioactivation process may produce toxic derivative
  • Concentration factor
    • Dependent on uptake, accumulation and excretion of toxin
  • Tissue-specific susceptibility to toxic insult
    • Based on anatomical and physiological differences between individual classes of cells
    • In sufficient amounts, many xenobiotics trigger an organ-selective pattern of toxicity
21
Q

What are the modifying factors in response to toxins?

A
  • Frequency of exposure to a toxin
  • Accumulation of toxins in the body
  • Duration of exposure to a toxin
  • Inter-individual differences in toxic responses
    - Genetic polymorphism in physiologically important genes

BI316 (13 decks)

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