Chapter 40 Toxicology
In the study of toxicology, a solid appreciation of pharmacokinetics and pharmacodynamics (see Chapters 14 to 19) is very important, as the mechanics of the two areas are very much a part of what makes a chemical harmful to a patient. Poisons or toxicants are chemicals that have harmful or adverse effects on living organisms. A chemical can be poisonous under one set of conditions and not under another. For example, potassium is a vital part of body metabolism, but too much will cause atrial fibrillation.
There are two different types of toxic reaction:
When dealing with chemicals, the following must be kept in mind:
The Occurrence of Poisons
Drug Absorption
Gut
This is a common route of entry. Different parts of the gut allow different rates of absorption:
Skin
• Factors Affecting Toxin Absorption through the Skin
Distribution and Transport
The Role of Blood
Enzymes
Chemicals can interfere with the enzymes that are vital as catalysts of metabolic processes in the body (see Chapter 19 ‘Pharmacodynamics: how drugs elicit a physiological effect’, p. 137):