Toxicology

Toxicology is defined as the study of poisons and its effect on organisms especially with the humans. It is also concerned with the study of the symptoms, mechanisms, treatment and detection of poisoning.  A poison is any substance which has adverse effects upon exposure.

Major disciplines of Toxicology

• 1.       Mechanistic – mimics the biochemical and cellular effects of toxins. Studies from this field provide a foundation for rational therapy design and development of tests aimed to assess degree of exposure of poisoned human.
• 2.       Descriptive- uses results from animal experiments  to see what level of exposure will cause damage to humans, this process is otherwise known as risk assessment.
• 3.       Forensic- this is concerned in medicolegal consequences of toxin exposure
• 4.       Clinical – deals with interrelationship of toxins to diseases.

*Other areas include: Aquatic , Chemical, Ecotoxicology, Environmental toxicology, and Medical toxicology.

Toxin Exposure

From a clinical point of view, exposure to toxins occur due to suicide(50%), accidents(30%) and the remaining percentage to occupational hazards and even homicide. Accidental exposure occurs more commonly among children and suicide-induced exposure produces the highest mortality rate.

Routes

• 1.       Ingestion- most commonly seen in clinical setting
• 2.       Inhalation
• 3.       Transdermal

Although harm produced by poisoning is due to poisons, other factors must be taken into consideration. One of the key factors in identifying the effect of poison is its dose.  In toxicology, any substance can cause harm if given at the correct dosage, this includes water. The dose of toxin is positively correlated to its effect. Although death is the most severe effect of poisoning, some toxins when given at small amounts can produce pathologic effects.

Dose-Response Relationship
Photo Credit:  http://www.fao.org/docrep/009/a0238e/A0238E26.gif 

Many agents have been encountered that can produce toxic effects to humans but here are some non-drug agents which are commonly encountered and presents medical emergencies in acute exposure:

1. Alcohol
2. Carbon Monoxide
3. Caustic agents
4. Cyanide
5. Metals and metalloids
6. Pesticides

Here are some therapeutic drugs that are most commonly seen in overdose:

1. Salicylates
2. Acetaminophen

Laboratory Testing

In most cases, analysis of toxic agents is a two-step manner:

1. Screening- rapid, simple, qualitative
2. Confirmatory- example is Thin Layer Chromatography 

Thin Layer Chromatography
Photo Credit:  http://www.waters.com/webassets/cms/category/media/other_images/primer_b_%20thinlayer.jpg 

References:
Clinical Chemistry: Techniques, Principles, Correlations
by: Bishop, Fody, Schoeff
http://www.news-medical.net/health/Toxicology-What-is-Toxicology.aspx