Pharmacology

2.1 INTRODUCTION

2.1.1 Learning the Language of Pharmacology

One of the diffi culties in learning about any medical fi eld is becoming familiar with

the technical jargon. Psychiatry is no different. Doctors like to use as few words as

possible but be as specifi c as they can possibly be. We accomplish this by taking

simple root words and adding one or more prefi xes and suffi xes to derive the specifi c

meaning that we want to convey. The result is that we can say a lot with a few words,

though at times it may sound as if we say little with a large number of words. The

lengthy words that sometimes arise when several scientifi c prefi xes and suffi xes are

added to a root word can be very imposing to those who are not initiated into

“doctor-speak.”

Let us share an example. The body’s hormone system is called the endocrine

system. Endocrine comes from a Greek prefi x that means “within” (endo-) and

a Greek root word that means “separate” (krinein). This makes sense when you

realize that hormones are substances that carry instructions between separate organs

within your body. By adding the suffi x -ologist (which means one who studies) to

endocrine, we get the term endocrinologist. An endocrinologist is simply a doctor

who studies and treats illnesses of the hormone system. But the hormone system

does not work alone; it functions in concert with other body systems such as the

nervous system. By adding the prefi x neuro- (which means nerve), we arrive at

the term neuroendocrinologist. A neuroendocrinologist is a doctor who studies the

interaction between the nervous system and the hormone system. When the hormone

and nervous systems interact, this has an impact on the way we think and behave.

In other words, it affects our mind. By adding the prefi x psycho- (which means

mind), we have the term psychoneuroendocrinologist. A psychoneuroendocrinologist

is one who studies how the mind is affected by the interaction between the

hormone system and the nervous system.

As you can see, by stringing several simple words together, we can construct

complex medical terms that can convey large amounts of information. We will try

to avoid using too many of these technical terms as we set off on our journey into

the study of (-ology) how medications (pharmaco-) affect the mind (psycho-). In a

word, let’s take a look at psychopharmacology.

2.1.2 Overview

Before we introduce you to the many psychiatric illnesses and the medications used

to treat these illnesses, you fi rst need a general understanding of just how these

medications work. In this chapter, we will introduce you to these concepts.

First, you will learn about the human nervous system and how it works when it

is healthy. This will include an introduction to the structure (anatomy) of the nervous

system and the function (physiology) of the nervous system. Next, we’ll describe

the things that can go wrong. We’ll look at how the system breaks down and malfunctions.

Then we’ll show you how these breakdowns can result in psychiatric

illness. Finally, we’ll introduce you to the medications used to treat psychiatric

illness. You will learn where these medications work and our best guess of how they

work. The presumed mechanism of action of many medications is just that, presumed.

In contrast to antibiotics, in which we know quite a lot about the ways that

they kill bacteria or stop them from reproducing and how these mechanisms ultimately

effect a cure for an infectious disease, less is known about how psychotropic

medicines work. Oh, we pretty well understand what psychotropic medicines do

when they reach the nerve cell. For example, most of the antidepressants used today

block the reuptake of serotonin at the nerve cell, but we’re still not sure why blocking

serotonin reuptake gradually improves mood in someone with depression. This

will lead to a “tour,” if you will, of what happens to a medication from the time the

pill is swallowed, until it exerts its therapeutic effect.

2.2 NORMAL HUMAN NERVOUS SYSTEM

There are two parts to this story: function and structure. The study of the body’s

structure is called anatomy, and so, we’ll be discussing neuroanatomy (the structure of the nervous system). The study of the body’s function is called physiology,

and so, we’ll also be discussing neurophysiology (the function of the nervous

system).

As architects teach us, form follows function. The layout of a building is dictated

in large part by its intended use. A hospital, an airport terminal, a restaurant, a

home, and a factory are each designed to serve a specifi c purpose. If the building’s

design does not facilitate its purpose, then it will soon be abandoned.

Similarly, the structure of the nervous system is interwoven with its function. At

all levels, from the microscopic highly branched nerve cell to the multiple connections

between large brain regions that are visible to the naked eye, the structure of

the nervous system is obviously designed to serve its chief purpose: communication.

As a result, it is diffi cult to talk about structure separately from function. Nevertheless,

a divided, stepwise approach may help make these complicated matters easier

for you to understand.

2.2.1 Neuroanatomy: Structure of the Nervous System

Central Nervous System (CNS). The human nervous system is an integrated

communication network that sends and receives information throughout the body.

This network is divided into two main divisions: central nervous system (CNS) and

peripheral nervous system (PNS). The CNS is the command center of this network

and is made up of the brain and spinal cord. The PNS is the interface of the nervous

system with the rest of the body and the external environment. It is comprised of

nerve fi bers and small clusters of nerve cells known as ganglia.

Neurologists treat nervous system diseases that mainly cause physical symptoms.

Therefore, they are concerned with both the CNS and the PNS. Mental health professionals,

on the other hand, treat diseases that produce emotional, thought, and

behavioral symptoms. As a result, we are more concerned with the CNS and, in

particular, the brain.

The Brain. The brain is the most magnifi cent of the body’s organs. But then, as

mental health professionals, we may all be a little biased. As you study the brain,

you learn very quickly that it is highly organized. If you cut the brain like a loaf of

bread, which we can now do visually with computed tomography (CT) and magnetic

resonance imaging (MRI) scans, there are many structures that are easy to see.

We’ll spare you all the details regarding these many brain regions.

Over the years, we have learned a great deal about the functions of each of these

structures. This knowledge has come about in several ways. First, we can look at

the effect of disease or injury in a particular part of the brain. For example, if a

stroke causes paralysis, then we can assume that the injured part of the brain was

responsible for movement of the paralyzed body parts. Likewise, if an injury results

in certain personality changes, then we can assume that the injured part of the brain

contributed to those behavioral alterations. One of the best-known examples is the

effect of a stroke upon mood. It is well known that a stroke to the left frontal area

of the brain dramatically increases the likelihood of depression. On the other hand,

a stroke to the right frontal area increases the likelihood of developing a manic

episode. Clearly then, the frontal lobes of the brain contribute to our mood state.

As an aside, depression following a stroke occurs in 25–45% of patients. It can be

easy to explain the vulnerability to depression after a stroke in terms of disability,

loss of independence, or a reminder of our mortality. Such explanations are sometimes

used to rationalize that medically ill patients have a “right” to be depressed

and therefore don’t need antidepressant treatment. However, depression following a

stroke, just like depression that may accompany a heart attack or cancer, should be

treated aggressively, and the option of medications should be considered. In fact, it

is often depressive episodes that occur in response to a stressor such as medical

illness that call for consideration of antidepressant therapy. The patient who becomes

depressed after a stroke or a heart attack is less likely to be successful in occupational

therapy, physical therapy, or making life-style modifi cations, such as dietary

changes or smoking cessation, that are important in reducing the risk of another

event.

We are now learning even more about the brain through the use of imaging

technology. MRI provides unbelievably detailed pictures of the brain’s structure.

Computer programs now allow us to use the MRI “slices” to construct threedimensional

views of the brain. The latest developments are the so-called

...