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Chemistry

Properties

This section covers the chemical and physical properties of key substance classes in toxicology

Alcohols

  • Definition: Organic compounds characterized by one or more hydroxyl (-OH) groups
  • Examples: Methanol, ethanol, isopropanol, ethylene glycol, propylene glycol
  • Key Properties
    • Polarity: The hydroxyl group makes alcohols polar
    • Solubility: Short-chain alcohols are miscible with water; solubility decreases with increasing carbon chain length
    • Boiling Point: Increases with increasing molecular weight and hydrogen bonding
    • Flammability: Alcohols are flammable
  • Toxicokinetics
    • Rapid absorption
    • Metabolism: Alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH)
    • Excretion: Urine and lungs
  • Toxic Effects
    • CNS depression, metabolic acidosis, organ damage

Heavy Metals (e.g., Lead)

  • Definition: Metallic elements with relatively high densities that are toxic at low concentrations
  • Examples: Lead (Pb), mercury (Hg), arsenic (As), cadmium (Cd)
  • Key Properties
    • Metallic Bonding: Good electrical and thermal conductivity
    • Variable Oxidation States: Can exist in multiple oxidation states
    • Complex Formation: Tendency to form complexes with biological molecules
    • High Density
  • Toxicokinetics
    • Absorption: Varies based on the metal and route
    • Distribution: Accumulation in specific tissues (e.g., bone, kidneys)
    • Metabolism: Some undergo biotransformation
    • Excretion: Primarily urine and feces
  • Toxic Effects
    • Enzyme inhibition, oxidative stress, organ damage, neurological effects

Analgesics (e.g., Acetaminophen)

  • Definition: Medications used to relieve pain
  • Examples: Acetaminophen, NSAIDs, Opioids
  • Key Properties
    • Structural Diversity: Wide range of chemical classes
    • Functional Groups: Hydroxyl, amino, carbonyl, carboxyl
    • Solubility: Varies depending on the specific drug
    • Acidic or Basic Character
  • Toxicokinetics
    • Variable absorption and distribution
    • Metabolism: Liver (CYP enzymes)
    • Excretion: Urine
  • Toxic Effects
    • Liver damage, gastrointestinal effects, respiratory depression

Drugs of Abuse

  • Definition: Substances used for non-medical purposes, often for psychoactive effects, which can lead to dependence and addiction
  • Examples: Opioids, stimulants, cannabinoids, hallucinogens, depressants
  • Key Properties
    • Structural Diversity: Wide range of chemical classes
    • Psychoactive Effects: Alter mood, perception, and cognition
    • Lipophilicity: Many are lipophilic
    • Solubility: Variable
  • Toxicokinetics
    • Variable absorption, distribution, metabolism, and excretion depending on the drug
  • Toxic Effects
    • Dependence, addiction, organ damage, neurological and cardiovascular effects |

Clinical Significance

  • Analytical Method Selection: Physical and chemical properties influence the choice of analytical methods
  • Toxic Effects: These properties influence how the substances are absorbed, distributed, metabolized, excreted, and interact with biological systems, ultimately affecting their toxicity
  • Sample Preparation: Understanding these properties helps optimize sample preparation
  • Exposure Assessment and Risk Evaluation: Knowing the sources and fate of these chemicals is important for assessing exposure risks