Toxicology

Definitions

Poison

A Substance capable of causing illness /death when introduced / absorbed

Xenobiotic

Foreign chemical substance

LD50

50% of the lethal dose

Fundementals of Toxicology

Exposure must occur first

Magnitude of risk is proportional to both potency, and extent of exposure

Certain chemicals cause non-specific damage by altering proteins, nucleic acids, lipids

Biotransformation of chemicals may result in reactive metabolites / free radicals / oxygen radicals

The dose makes the poison - Toxicity determined by amount of chemical at target site

Mechanism of Toxicity

  1. Inflammation and immune mediated

Penicillin

  1. Altered enzyme and receptor function

Organophosphates

3.Organ directed damage

Acetaminophen, methanol, alcohol, cigarette smoke

  1. Human development - Teratogens

Alcohol, Thalidomide

Inflammatory and Immune Mediated Toxicity

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Organophosphates

Mechanism of Toxicity

Altered enzyme function

  1. Serine residue of AChE phosphorylated and ages
  1. ROH group replaced by hydroxyl
  1. Stable and irreversible ageing (can be reversed if caught early enough)

Antidote

Pralidome

  1. Breaks bond between organophospate and serine
  1. Release of organophosphate and regeneration of serine hydroxyl group on AChE

Symptoms

Lacrimation 💧

Muscle paralysis 🗽

Diarrhoe 💩

Paracetomol Overdose

Mechanism of Toxicity

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