PHAR 380.  Queens University PHAR 380

PHAR 380
Module 1
Section 1: general principles of toxicology
Introduction to the principles of toxicology
- Dose, duration of exposure, and frequency of exposure to a toxicant, as well
as differences between exposed individuals, affect the toxic response that is
seen following exposure to a chemical
What is toxicology?
- Toxicology is the basic science of poisons
- Modern toxicology was founded by Paracelsus (1493-1541) who is known
for saying: “all substances are poisons: there is none which is not a poison.
The right dose differentiates a poison and a remedy”
- Toxicology can be found in everything. Even substances that are thought to
be harmless or even beneficial such as waster can end up producing a toxic
response if taken in a high enough dose
- While it is extremely difficult to consume enough water to produce a toxic
response, the idea that even water can produce a toxic response
emphasizes that people walk a fine line in their day-to-day lives with the
numerous commercial products used to enhance their lives
- Example: perhaps you thought something that is in the news- opioids for
example. You know that opioids such as morphine are incredibly effective
and useful drugs to alleviate pain. But as you tragically hear on the news on
a weekly basis Canadians are being exposed to toxic and fatal doses of
opioids at an alarming rate
Common toxicology definitions
- Toxicity: the quality of being toxic or poisonous. Toxicity is caused by
exposure to a substance either a toxicant or toxin
- Toxicant: is a substance that will produce a harmful effect when
administered to an organism
- Toxin: is a toxicant produced by a living organism. All toxins are toxicants,
whereas not all toxicants are toxins
- Xenobiotic: is a chemical that is foreign to the body. It doesn’t have to be
toxic just not endogenously produced