Toxicology: Key Concepts

• Toxicology is introduced as the study of harmful effects of substances on living organisms.

Important concepts in toxicology:

• Adverse Effects: Harmful effects indicated by mortality, changes in food consumption, body/organ weights, enzyme levels, or pathologic findings.
• Clastogenesis: Chromosome breakage leading to rearrangement, loss, or addition of chromosome parts, potentially linked to chronic inflammatory disorders.
• Haptens: Small molecules (under 1000 MW) that bind to carrier molecules to become antigens, causing an immune response; urushiol is an example in poison ivy.
• Mutagenesis: Alteration of an organism's genetic information, causing heritable changes in nucleic acids; examples include vinca alkaloid, bromine, and nicotine.
• Selective Toxicity: A chemical injures one type of living matter without harming another, even with intimate contact.
• Teratology: Study of malformations induced during development from conception to birth.
• Toxic: Synonymous with "harmful" in terms of chemical effects.
• Toxicity: A relative term used to compare the harmful effects of different chemicals.
• Toxin: Toxic substances produced naturally.
• Toxicodynamics: Altered drug pharmacodynamics at toxic dosages due to changes in normal receptor and effector mechanisms.
• Toxicokinetics: How the body handles toxic doses of chemicals, affecting absorption, metabolism, or excretion.
• LD50 (Median Lethal Dose): The dose required to cause 50% mortality in a population.
• Toxidromes: Clinical syndromes essential for recognizing poisoning patterns, characterized by signs and symptoms suggesting a specific class of poisoning.
• Examples of toxidromes include:
  • Sympathomimetic
  • Sedative Hypnotic
  • Opiate / opioid
  • Anticholinergic
  • Cholinergic

Fetal Alcohol Syndrome

• A condition in a fetus characterized by small head, short nose, small eye openings, and thin upper lip

Risk

• Expected frequency of an untoward effect in response to a particular agent.
• Threshold Limit Value (TLV): Acceptable exposure amount for a given agent over a period of time.
• Carcinogenicity (Tumorigenicity): An agent's ability to cause cancer.
• Lethal/Fatal Dose: Quantity of a substance that can cause death.
• Intoxication: Toxicity associated with any chemical substance.
• Poisoning: Clinical toxicity resulting from accidental exposure.
• Overdose: Intentional exposure causing self-injury or death.
• Poisons: Substances with almost exclusively harmful effects.
• Acute exposure: Generally, a single dose. Repeated exposures are usually dietary
• Subacute exposure: Repeated exposure for a month or less
• Subchronic exposure: Repeated exposure for 1 to 3 months
• Chronic exposure: Exposure for greater than three months

Types of Poisoning:

• Acute Poisoning: Prompt and marked disturbance or death caused by a strong poison in a single dose or several small doses over time.
• Chronic Poisoning: Gradual deterioration of tissue function, which may or may not result in death.

Action of Poisons:

• Local: Changes or disturbance produced at the point of contact with the poison.
• Remote: Changes or disturbance produced in a distant part away from the site of application.
• Combined: Effect is not only localized at the point of contact but also affects remote organs.

Acute and Chronic Exposures:

• Benzene acute exposure leads to CNS Narcosis, but chronic exposure leads to Bone Marrow Damage and Leukemia.
• Cigarette smoke acute exposure leads to Nervous system stimulation, but chronic exposure leads to Cancer of mouth, pharynx, larynx, lung, esophagus, pancreas, and bladder, emphysema.