Toxicology and its Division
“All substances are poisons. There is none
which is not a poison. The right dose differentiates a poison & a remedy.” - Paracelsus
1532
This quote explains that the probable for harm is prevalent and
all substances could be toxic but the level of damage that a chemical can cause
on a human depends on the dose or the degree of contact or exposure and on
other factors. In other words the danger from a toxic substance depends on the contact
or exposure.
My
blog is intended for those with slight or no background at all in toxicology.
Toxicology is a difficult and complex science. It is the the study of
adverse effects on humans of prophylactic & therapeutic drugs, food &
beverage additives, and industrial chemicals incorporated into consumer
products.
Terminologies used in Toxicity
Screening:
acute toxicity
§
administration
of progressively larger single doses up to the lethal dose
§
“No-Effect”
dose – largest dose at which a specific toxic effect is NOT seen
§
Minimum Lethal
Dose – smallest amount of the drug that can kill a study animal
§
LD50 – dose
that kills half of the experimental animal population
§
Toxic dose –
dose that kills the patient.
§
Subtherapeutic
dose – dose that has no effect.
§
Therapeutic
dose – dose that cure the patient.
subacute / chronic
toxicity
§
administration
of multiple doses to detect any adverse effects
mutagenicity –
§
detection of
possible ability to induce genetic alteration (mutation)
carcinogenicity
–
§
detection of
possible ability to induce abnormal clonal uncontrolled proliferation of
genetically altered cells
teratogenicity
–
§
detection of
possible deleterious effects on the developing fetus
“Local”
refers to the site of action of an agent and means the action takes place at
the point or area of contact. The site may be skin, mucous membranes, the
respiratory tract, gastrointestinal system, eyes, etc. Absorption does not
necessarily occur. Examples: some strong acids or alkalis.
“Systemic”
refers to a site of action other than the point of contact and presupposes
absorption has taken place. For example, an inhaled material may act on
the liver. Example: arsenic affects the blood, nervous system,
liver, kidneys and skin.
Cumulative
poisons are characterized by materials that tend to build up in the body
as a result of chronic exposure. The effects are not seen until a
critical body burden is reached.
Example: heavy metals (such as Lead).
Synergistic
responses: When two or more hazardous material exposures occur, the
resulting effect can be greater than the effect of the individual
exposures. Example: exposure to both asbestos and tobacco smoke, producing lung
cancer or mesothelioma.
To make it simple, here are some classification and examples
of chemical hazards in the workplace and in the environment.
Category
|
Examples
|
Metals, and metalloids
|
arsenic, cadmium, lead, mercury, nickel, tin, etc
|
Inorganics
|
asbestos, carbon monoxide, hydrogen sulphide
|
Hydrocarbons - aliphatic
|
propane, butane, pentane, hexane
|
Aliphatic
alcohols, ketones, ethers, aldehydes and acids
|
ethyl alcohol (ethanol), acetone, diethyl ether, formaldehyde,
acetic acid
|
Hydrocarbons - aromatic
|
benzene, toluene, xylene, naphthalene
|
Phenols
|
phenol, pentachlorophenol
|
Chlorinated volatile organic compounds
|
Perchlorethylene,(tetrachloroethene), trichloroethylene
(trichloroethene), vinyl chloride
|
Chlorinated non volatile organic compounds
|
chlorinated dioxins and dibenzofurans, polychlorinated
biphenyls, pesticides such as chlordane and DDT
|
Miscellaneous organic compounds
|
acrylonitrile, benzidine, aniline, di-isocyanates,
organophosphates
|
Hope my
introduction gave you a lot of knowledge about the basic of Toxicology and it
made you interested about the subject. Toxicology is a very exciting topic to talk
about. Let’s now proceed to the divisions of Toxicology.
Divisions of
Toxicology:
1. Drugs of
abuse - drugs or chemicals which are taken repeatedly in a pattern &
amount that interferes with one’s health or normal function. It have
multiple effects, usually producing a feeling of well-being in the user and
repeated use can lead to higher & higher dose needed to replicate the
feeling causing emotional dependence, & in some, true physical dependence.
Here are some examples:
a. Stimulants - drugs that "stimulate" or accelerate the central nervous system; usually sympathomimetic Ex: Caffeine, Nicotine, Cocaine, Crack, Ecstasy, Amphetamines, Methamphetamines.
b. Hallucinogens - natural or synthetic drugs that can produce hallucinations when taken. Ex: LSD, PCP, DMT, DOM (STP), Psilocybin (“magic mushrooms”), Peyote cactus, Mescaline, Marijuana, Ecstasy, and Ketamine.
c. Cannabis - Cannabis is a collective term used to describe hemp plants that are smoked and ingested to produce psychophysical changes when ingested. Ex: Marijuana, hash, and hash oil.
d. Depressants - drugs which have a sedating effect upon the central nervous system.
e. Opiates & Opioids- narcotics that have a depressant effect upon the user. Ex: Heroin, Meperidine (Demerol), Morphine, Hydromorphone and Codeine.
f. Sedative–Hypnotics - relaxants, induce sleep: Ex: Ethyl alcohol; anti-anxiety agents-tranquilizers: benzodiazepines Diazepam, Rohypnol; nonbarbiturates- Halcion, Quaalude; long-acting barbiturates – Phenobarbital; short-acting barbiturates – Seconal.
g. Anabolic Steroids - Anabolic steroids are drugs or hormones akin to testosterone that increase muscle growth. Ex: Halotestin, Maxibolin, Anavar, and Dianabol.
h. Volatile substances / Inhalants - give off fumes for a high Ex: glue, aerosols, solvents.
i. Laxatives - usually abused for weight loss Ex: Bisacodyl, Danthron, Phenolphthalen, Rhein.
2. Emergency Toxicology
- deals
with emergencies such as poisonings, attempted suicides and overdoses.
Image Credit: http://www.globalpackagegallery.com/main.php?g2_view=core.DownloadItem&g2_itemId=64441&g2_serialNumber=2
3. Forensic
Toxicology - Medico-legal aspects of poisonings. Establish relationship
between tissue residual level and probable cause of death as well as identification
and quantification of poisons.
4. Industrial
Toxicology - is a science
that deals with potential harmful effects of materials, products and wastes on
health and environments.
Image
Credit: http://health.usf.edu/NR/rdonlyres/8F309F0B-7F97-42EC-9842-6D33CB7E6EB1/0/industrial.jpg
5. Therapeutic Drug Monitoring - is the measurement of specific
drugs at timed intervals in order to maintain a relatively constant
concentration of the medication in the bloodstream. Clinical application of Pharmacology; the
rational use of drugs in the treatment of diseases.
Before I end my blog, here's a sample movie about forensic toxicology..
Video Credit: http://www.youtube.com/watch?v=y9X1bwt0-TI
Thank
you for spending your precious time in reading my blog. Hope I’d helped you a
lot and motivated you to study about Toxicology.. ^^
References:
M. Bishop; Clinical Chemistry:
Principles, Procedures, Correlations
D. Calbreath; Clinical Chemistry: A
Fundamental Textbook
9:23 PM |
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