TOXICOLOGY

• Toxicology is a branch of pharmacology that deals with the undesirable effects of chemicals on living systems, from individual cells to complex ecosystems.
• The study of toxicology involves the adverse effects of xenobiotics and chemicals on living organisms.
• Toxicology is concerned with the deleterious effects of these chemical agents on all living systems.
• The term toxicology originates from the Greek word toxicon.
• Poison is any agent which may cause serious body injury, disease or death when applied, introduced into, or developed within the body.
• Toxin refers to toxic substances produced naturally.
• Botulinum toxin is produced by Clostridium botulinum.
• Tetanus toxin is produced by Clostridium tetani.
• Diphtheria toxin is produced by Corynebacterium diphtheriae.
• Receptor Tolerance is when the same amount of chemical reaches the site, but the target receptor response is decreased, for example, Nicotine in cigarettes can result in receptor tolerance.
• Receptor antagonism is when chemicals compete for the same receptor, decreasing effective binding of the toxic compound, for example, Naloxone and Morphine can result in competitive antagonism.
• Dispositional antagonism is when the disposition of a toxic chemical is changed so that concentration and/or duration is diminished.
• Synergistic chemical interactions result in combined effects that are much greater than the sum of effects when given alone, for example, Pyrethroids + Piperonyl butoxide (PBO) can result in pesticide synergism.
• Antagonism is when co-administration of two chemicals interferes with the toxicity of both or one of them, for example, Vitamin K can be an antidote for anticoagulant toxicity.
• Additive chemical interactions result in a combined effect that is the same as the sum of effects when given alone, for example, Alcohol + Benzodiazepine can produce a CNS depressant effect.
• Muscarine is produced by Amanita muscaria and phalloides.
• Potentiation is when exposure to a chemical with no toxicity increases the toxicity of another compound, for example, Isopropanol + carbon tetrachloride can result in greater liver damage.
• Dispositional Tolerance is when a decreased amount of chemical reaches the site where the effect is produced.
• Tolerance is a state of decreased responsiveness due to a prior exposure to the same or a structurally similar chemical in an individual, for example, there is a diminished response to a drug due to repeated exposure.
• Corrosives and irritants act locally and little goes systemic.
• Types of antagonism include functional, where chemicals counterbalance each other by exerting opposite effects on a physiological function, and chemical (or inactivation), where a chemical reaction between two compounds leads to less of the toxic compound.
• Bufotoxin is produced by frogs.
• Atropine is produced by Atropa belladonna.
• Abrin is produced by rosary pea.
• Idiosyncratic Reactions occur in individuals who have genetic polymorphisms that lead to structural changes in biomolecules, making them very sensitive or insensitive to a chemical.
• A broad range of effects can be found with many drugs or chemicals with sufficient exposure.
• Allergic Reactions occur when a person's immune system reacts to substances in the environment that do not bother most people, often requiring binding of chemical (hapten) to endogenous protein in order to be recognized by the immune system.
• Acute exposure is usually produced by taking small doses for a protracted period of time.
• Irreversible effects are not affected by tissue regeneration.
• Injection bypasses the protection provided by the intact skin and provides direct access in the bloodstream, making it the most dangerous route of exposure.
• Immediate toxicity is when most chemicals exert their effects soon after exposure.
• Local effects are limited to a specific area of the body, while others are systemic.
• Duration and frequency of exposure can affect the outcome of chemical exposure.
• Acute exposure to Cigarette Smoke can cause Nervous system stimulation, while chronic exposure can lead to Cancer or mouth, pharynx, larynx, lung, esophagus, pancreas, and bladder, emphysema.
• Taking only toxic doses of the drug is another method of acute exposure.
• Subacute exposure is characterized by repeated exposures usually dietary.
• Chronic exposure is exposure for greater than three months.
• Olfactory fatigue may occur when exposed to high concentration and prolonged exposure.
• Delayed toxicity may be immediate or delayed for days to years.
• Acute exposure to Benzene can lead to CNS Narcosis, while chronic exposure can cause Bone Marrow Damage and Leukemia.