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)

§  detection of possible ability to induce abnormal clonal uncontrolled proliferation of genetically altered cells 
§  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.

Metals, and metalloids 
arsenic, cadmium, lead, mercury, nickel, tin, etc
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
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.

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.

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..
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.. ^^

M. Bishop; Clinical Chemistry: Principles, Procedures, Correlations
D. Calbreath; Clinical Chemistry: A Fundamental Textbook

Comments (0)