If you are a big fan of Batman, you might be familiar with Poison Ivy, one of Batman and Robin's most powerful enemies. Her real name is Pamela Lillian Isley. Poison Ivy is obsessed with plants and with the environment in general. Instead of blood, chlorophyll flows through her veins giving her the power of toxic touch as well as the ability to make use of mind controlling pheromones for her criminal acts. Her first kiss is poison while the second one is the antidote to it. Her goal in life is to eradicate humanity so as to relieve the world of pollution.
Image Credit: http://www.ohio-nature.com/image-files/poisonivy2.jpg
Of course, in real life, poison ivy is just a plant-- a POISONOUS one. When this plant is bruised, damaged or burned, it releases an oil, urushiol which when it comes in contact with our skin, triggers an allergic reaction referred to as contact dermatitis. In most people, the allergy is in a form of an itchy, red rash with blisters or bumps. Burning this plant is very dangerous because the allergens may be inhaled. Inhalation may lead to lung irritation. Indeed, toxic substances are part of our lives. We should have enough knowledge about them in order for us to avoid the different risks that they impose.
Definition and Disciplines
What is TOXICOLOGY? If I were asked, I would say that it is a branch of science that deals with the study of poisons and the adverse effects of these substances to the human body. It is said that these is a very broad body of knowledge. Within toxicology, there are four disciplines being studied:
- Mechanistic Toxicology- studies the cellular and biochemical effects of toxins. This discipline provides a basis for rational therapy design. Also, in order to determine the degree of exposure of poisoned individuals, tests are being developed in this field.
- Descriptive Toxicology- animal experiments are being done in this field (risk assessment). The results are then used to predict what level of exposure will harm humans.
- Forensic Toxicology- this field establishes and validates the performance of methods that can be used to generate evidence in legal situations (death, etc.). Also, the major focus of forensic toxicology is the medicolegal consequences of toxin exposure.
- Clinical Toxicology- field which involves both diagnostic testing and therapeutic intervention. The relationship of toxin exposure and disease states is the focus of this field.
Toxin Exposure
People are exposed to toxic substances for various reasons. These include:
- Intentional suicide attempts (50%)- this has the highest mortality rate.
- Accidental exposure (30%)- occurs most frequently in children but also occurs in adults (therapeutic or illicit drug overdose).
- Homicide
- Occupational exposure- occurs primarily in industrial or agricultural settings.
Routes of Exposure
Toxins can enter the body through the following routes:
- Ingestion
- Inhalation
- Transdermal Absorption
Acute Vs. Chronic Toxicity
These two terms are used to describe the effect of a drug based on the duration and frequency of exposure. Acute toxicity is associated with a single, short-term exposure to a substance. The dose is sufficient to cause an immediate effect which is toxic. When there is a repeated, frequent exposure to a drug for extended periods of time (especially if the dose is insufficient to cause an immediate acute response), chronic toxicity may occur. This type of toxicity is often related to an accumulation of the toxic substance.
Terminologies
Of course, in order for us to understand toxicology better, we should be familiar with some terms that are commonly used in this field.
- Dose- this is the quantity of a substance, such as a drug, taken in.
- Dose-Response Relationship- this is the relationship of a dose of a drug taken by a person and the effect it exhibits on that individual. It is said that the dose and the response are directly proportional so the higher the dose, the greater the response exhibited.
- No-Effect Dose- the maximum dose wherein a toxic effect is not seen.
- Minimum Lethal Dose- this is the minimum dose that could kill an experimental animal.
- Median Lethal Dose- the dose that kills half of the population of the experimental animals.
Toxicology of Specific Agents
Some drugs, though they are not considered as toxins, that we encounter on a regular basis have potential adverse effects.
- Alcohol
- a central nervous system (CNS) depressant
- high levels of exposure can cause death
- may cause disorientation, confusion and euphoria
- continuous intake may progress to unconsciousness and paralysis
- recovery is rapid and complete after exposure ceases
- Carbon Monoxide
- a colorless, odorless and tasteless gas
- combines with the hemoglobin in the blood to produce carboxyhemoglobin (COHb)
- produced by incomplete combustion of carbon-containing substances
- net effect is tissue hypoxia
- people who die of carbon monoxide poisoning actually die due to lack of oxygen
- Cyanide
- binds to iron containing substances (e.g. hemoglobin and cytochrome oxidase) resulting to tissue and cellular hypoxia
- a supertoxic substance that can be in a form of a solid, gas or in solution
- has "odor of bitter almonds"
Metals
Metals, when ingested in large amounts and absorbed in their ionized forms, can be toxic to the human body.
- Arsenic
- has high affinity to the thiol groups in proteins
- has the "odor of garlic" and expresses a "metallic taste" when accidentally eaten
- sulfhydryl enzymes in the body are inhibited due to this metal
- a common agent of heavy metal poisoning
- Cadmium
- being a pigment of paints and plastics, it is an environmental pollutant
- when acidic foods are stored or prepared in containers made up of cadmium, cadmium poisoning can result upon ingestion of these foods
- type 1 epithelial cells in the lungs are destroyed and there is a decreased resistance to bacterial infections
- Lead
- metal that has the ability to bind with the matrix of bones and stay there for a long time
- has a half-life of 32 years
- encephalopathy, birth defects and compromised immunity are the results of exposure to this metal
- behavioral changes are the results of low-level exposure
- produces anemia by affecting the vitamin D and heme synthesis pathway of the blood
- Mercury
- an enzyme inhibitor
- has the ability to bind with proteins (like arsenic)
- can accumulate in the CNS once inhaled due to its ability to pass through the blood-brain barrier
- presence in the blood may result to loss of glomerular integrity
Drugs of Abuse
- Amphetamines
- treats narcolepsy and attentional deficit disorder
- related to dopamine and the cathecolamines
- sign of acute intoxication is hyperpyrexia
- hypertension, pancytopenia, cardiac arrhythmias and convulsions are its toxic effects
- Annabolic Steroids
- associated to testosterone
- increases muscle mass but large amounts cause chronic hepatitis, cardiomegaly and atherosclerosis
- Cannabinoids
- marijuana and hashish are examples
- tetrahydrocannabinol (THC) is the most potent component of marijuana
- THC induces a sense of well-being and euphoria but also causes impairment of intellectual functions
- Cocaine
- a local anesthetic for nasopharyngeal surgery
- a CNS stimulant that elicits a sense of excitement and euphoria
- direct toxicity on myocardium causes death
- not an addictive drug
- large amounts bring about violent behavior
- Prozac can inhibit the action of this drug
- Opiates
- derived from opium poppy
- naturally occurring substances include: opium, morphine (powerful analgesic) and codeine (antitussive)
- heroin is a modified form and is highly addictive
- exposure to large amounts lead to myoglobinuria, respiratory acidosis and cardiopulmonary failure
- Phencyclidine (PCP)
- an illicit drug that has stimulant, depressant, anesthetic and hallucinogenic properties
- toxic effects include stupor and coma
- Sedative Hypnotics
- CNS depressants but have therapeutic roles
- have the ability to potentiate the effects of heroin
- large amounts cause respiratory depression
- barbiturates and benzodiazepines are examples
Therapeutic drugs
Therapeutic drugs, such as acetaminophen and salicylates, when taken in large amounts also have adverse effects.
- Salicylates/ Aspirin
- an analgesic, anti-inflammatory and antipyretic drug
- has anticoagulant property
- may lead to metabolic acidosis and respiratory alkalosis when taken in large amounts
- Acetaminophen
- prostaglandin metabolism inhibitor
- overdosage leads to hepatotoxicity
Indeed, toxicology is an important field of medical science. Just imagine how short life would be if we are not aware of the adverse effects of the different drugs that we take. Knowledge of the different drugs and their effects is crucial if we want to have a long life. Remember what Paracelsus once said, "All things are poisons, for there is nothing without poisonous qualities. It is only the dose which makes a thing poison."
Thanks for reading my post! Wait for the next one! :)
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REFERENCES:
- Clinical Chemistry: Techniques, Principles, Correlations 6th Ed. by Michael L. Bishop et al. (2010)
- Clinical Chemistry Review Handbook for Medical Technologists by Maria Teresa T. Rodriguez (2010)
- Basic and Clinical Pharmacology 11th Ed. by Bertram G. Katzung et al. (2009)
- http://batman.wikia.com/wiki/Poison_Ivy_(Batman:_Arkham_Asylum)
- http://www.cdc.gov/niosh/topics/plants/
- http://www.grc.org/programs.aspx?year=2011&program=toxicity
- http://www.goodreads.com/quotes/show/214022
![http://www.nvcc.edu/loudoun/library/hottopics/MPj03961190000[1].jpg](http://www.nvcc.edu/loudoun/library/hottopics/MPj03961190000[1].jpg){kind=link}
