Toxicology

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:









Drug Absorption


The tissues that are most susceptible are those directly in contact with the environment, e.g. skin, mucous membranes of the lungs and gut.



Gut


This is a common route of entry. Different parts of the gut allow different rates of absorption:










Distribution and Transport



The Role of Blood





The brain, cerebrospinal fluid and developing fetus are separated by a protective layer of cells from the blood (Chapter 16 ‘How do drugs get into cells?’, p. 126). However, the placenta is not a very effective barrier to the entry of toxic chemicals. Many toxins enter the fetus by diffusion, e.g. thalidomide. Herbs containing volatile oils are thought not to be advisable for use during pregnancy as they can easily pass through to the fetus.


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Jul 22, 2016 | Posted by in PHARMACY | Comments Off on Toxicology

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