Apply basic knowledge of
pharmacology
Defining pharmacology
2
What is a drug?
4
The impact of psychoactive drugs on the body
6
The process by which psychoactive drugs act on the body
8
Drug groups
11
How are drugs named?
12
How are individual drugs classified?
14
Common terms relating to the action of drugs
19
Summary
26
Additional resources
28
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Defining pharmacology
Activity 1: Pharmacology—unravelling some terms
There are a number of terms you need to understand as part of developing an awareness of
drug actions. Use a good dictionary to look up the following words (eg The Macquarie
Dictionary). Write down the meaning of each, then compare your definitions with those in
the feedback given after the activity.
1
Pharmacy
_____________________________________________________________________
2
Pharmacology
_____________________________________________________________________
3
Pharmaceutical
_____________________________________________________________________
4
Pharmacist
_____________________________________________________________________
5
Pharmacologist
_____________________________________________________________________
6
Pharmakenetics
_____________________________________________________________________
7
Pharmacopeia
_____________________________________________________________________
2
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Feedback 1
Pharmacy—the art or practice of preparing and dispensing drugs
Pharmacology—the science or knowledge of drugs and their action on living
systems
Pharmaceutical—that which relates to pharmacy
Pharmacist—one who is skilled in pharmacy
Pharmacologist—one who is skilled in the science of drugs and their actions
on living systems
Pharmakeneticsn—the study of how drugs interact with each other
Pharmacopeia—a book containing a list of drugs that contains information
about their preparation, properties, actions and uses
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What is a drug?
If pharmacology is the study of drugs, then what is a drug? For example,
should vitamin tablets and even water be considered a drug? What about
coffee and chocolate; where do they fit in?
Activity 2: Perceptions about drugs
1
What is a drug? List the thoughts and images that come into your mind when you think
about the term ‘drug’. You may like to use words or draw pictures.
2
Now reflect on what you have produced. Where did you get these images and ideas?
The media? Friends?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
4
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Feedback 2
One definition of ‘drug’ is ‘any chemical substance which alters the way
your body or your mind works’ (Centre of Education and Information on
Drugs and Alcohol—CEIDA). Definitions will vary, though they are usually
inclusive of the idea that a drug is a substance (be it vegetable, animal or
mineral) used in the preparation or composition of medicines.
A drug, to many people, is something that is illegal and taken by people who
have ‘problems’. This of course could not be further from the truth. Yet, go
to the pub and ask for a drug and you may be thrown out. Ask for a glass of
‘the drug, beer’ and I’m sure that you will get some very strange looks.
Alcohol is a drug as are cigarettes, though many people don’t see or refer to
them as such. Drugs, to many people, refer to substances that are illegal.
Would you now add some more types of products to your list of drugs, such
as coffee, tea, chocolate and Coca-Cola?
Krivanek (1988) suggests that we should not get too hung up on definitions
of what a drug is. She suggests that, in the end, the most appropriate
definition of a drug is whatever a person considers a drug to be.
This topic is specifically focused on the drugs that are more commonly used
and abused in the alcohol and other drugs (AOD) field. These drugs are
referred to as psychoactive drugs. Psychoactive drugs are substances that
affect and alter mood, cognition and behaviour and affect the central
nervous system (CNS), which comprises the brain and the spinal cord.
Psychoactive drugs are sometimes referred to interchangeably as
psychotropic (an agent that can produce symptoms similar to those of the
nervous system) and neuroleptic (exerting an effect on the mind) drugs. In
this topic we will only use the term psychoactive.
Activity 3: Identifying psychoactive drugs
Think about the term ‘psychoactive drug’. It affects mood, cognition (thinking processes)
and behaviour. List some drugs that you know affect these things. They can be legal or
illegal.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
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Feedback 3
There are a huge number of psychoactive drugs—your list may have
included alcohol, heroin, tranquillisers, methadone, cannabis, inhalants,
solvents, caffeine, tobacco, amphetamines (speed), LSD, magic mushrooms
and ecstasy, to name just a few.
The impact of psychoactive drugs on
the body
Essentially, psychoactive drugs have an impact upon the way people feel
emotionally (mood), the way in which people think (cognition), and the way
in which people act (behaviour). The impact of psychoactive drugs on
mood, cognition and behaviour will, of course, depend on many factors,
including:

the drug itself

the way in which it is used (eg orally, intravenously)

the frequency of drug use

the quality of the drug

the individualdifferent people may have differing responses to the
same drug.
Activity 4: Effects of psychoactive drugs
Consider the following two scenarios and answer the questions about each:
1
Tom has been drinking in the local pub for the past three hours. He has been
consuming three schooners of beer an hour. So after three hours he has had quite a bit
to drink (approximately nine schooners). Tom has just received a pay rise and feels on
top of the world.
In terms of the effect of this psychoactive substance, alcohol, how would Tom’s mood
(the way he feels), cognition (the way he thinks) and behaviour (the way he acts) be
different from when he first entered the pub?
(a) Tom’s mood (the way he feels) might be?
_____________________________________________________________________
_____________________________________________________________________
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(b) Tom’s cognition (the way he thinks) might be?
_____________________________________________________________________
_____________________________________________________________________
(c) Tom’s behaviour (the way he acts) might be?
_____________________________________________________________________
_____________________________________________________________________
2
Allan, Tom’s friend, has also been drinking about the same amount of beer
(approximately nine schooners over three hours). Unfortunately, Allan has been
unemployed for the past three months and just this week has been to seven job
interviews, all of which have been unsuccessful. Answer the following questions in
relation to Allan.
(a) Allan’s mood (the way he feels) might be?
_____________________________________________________________________
_____________________________________________________________________
(b) Allan’s cognition (the way he thinks) might be?
_____________________________________________________________________
_____________________________________________________________________
(c) Allan’s behaviour (the way he acts) might be?
_____________________________________________________________________
_____________________________________________________________________
Feedback 4
There may be some similarity between the amount of beer that Tom and
Allan have drunk, yet the way both these men feel, think and act may be
quite different. The impact of receiving a pay rise (Tom) or being
unemployed (Allan) may play a big part in the way in which alcohol affects
these two people.
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The process by which psychoactive
drugs act on the body
Every thought, emotion and action that we experience involves the central
nervous system. This system includes the brain and spinal cord and has an
impact on the nerves that extend throughout the entire body. The brain is
made up of billions of nerve cells, called neurons, which are tiny
communication pathways, responsible for sending messages to each other at
speeds of up to 300 km/h. The brain weighs approximately 1.5 kg and is
more complex than the world’s most sophisticated computer.
Figure 1: Diagram of a nerve cell
Consider what occurs within your brain when you need to write a shopping
list. Go through the motions really slowly …
You look for the penyour eyes see the pen (you have the memory of what
a pen is) and relay this information to the visual centre at the back of the
brain. A message gets sent through the CNS to pick up the pen, which you
do. Then, you start to identify the things that are needed for the next few
days and write them down. At the same time, you are remembering how
much money you have available and how often you will be at home over the
next few days. While doing your shopping list you may be listening to the
radio, talking to someone else and thinking about something you did
yesterday. All of this is happening in the space of seconds. Throughout this
process of making a shopping list, there is a huge amount of activity
occurring in your brain. The nerve cells or neurons that transmit messages
from one part of the brain to another do so by sending electrical charges
down the nerve pathways. The messages get sent down nerve cells by a
combination of electrical and chemical means. The chemical means are
called neurotransmitters. When a neurotransmitter is released it crosses the
synapse and fits into what is called the receptor located at the other nerve
membrane. The neurotransmitter has a shape that fits directly into the shape
available in the opposite membrane, much like a key into a lock. When the
neurotransmitter and membrane combine they initiate a reaction.
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Look at the diagram below and highlight the following:
1
neurotransmitter
2
receptor
3
synapse
4
axon.
Figure 2: Close up of receptors and neurotransmitters
You now have some understanding of how the neurons or nerve pathways in
the brain work. The next thing to consider is what happens when a
psychoactive drug is introduced into the body. That is, what happens at the
level of the CNS. When psychoactive drugs enter the bloodstream and reach
the CNS, there are two main ways that they affect the nerve cells of the
CNS:

by attaching themselves to points (receptors) on the nerve cell

by interfering with the brain chemicals in the gap (synapse) between the
nerve cells.
The ways in which drugs act on the brain are quite complex. Now that you
have read some material on the CNS and its components let’s see how clear
your understanding is of how psychoactive drugs affect it
Consider the following scenario:
A person takes a large quantity of speed by snorting the drug. In your own
words, how could you explain why the person experiences the effects of this
drug? In other words, what is happening? When a person snorts speed, the
drug rapidly enters the blood stream and travels to the CNS. Once at the
level of the nerve cells (neurones), several things will happen. Firstly, the
drug will be taken into the nerve cells at the receptor sites and, secondly, it
will interfere with the normal production and mix of brain chemicals
(neurotransmitters) in the space between the nerve cells (synapse).
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What this will do is increase the messages that travel along the nerve cells
(electrical) and across the space between the nerve cells. So speed will
mimic the effect of naturally occurring brain chemicals and speed up activity
at the level of the CNS. Thus, we will see a person whose speech, actions
and thoughts are sped up.
In summary: It is the way in which psychoactive drugs act on the neuron
(nerve cell) and also the manner in which psychoactive drugs interact with
the brain chemicals (neurotransmitters) that produce the effects that are seen
when people take these drugs.
Web visit
Understanding the CNS is a complex and difficult task. If you find it
difficult it would pay to go to either your TAFE or local council library and
find some books that will provide you with additional reading, or have a
look on the Internet.
Key words for your search will include:
10

anatomy and physiology of the human body

anatomy and physiology of the central nervous system

central nervous system

the brain and how it works.
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Drug groups
It is quite important that you are able to identify different drugs in terms of
the psychoactive drug group that they belong to. There are three main
psychoactive drug groups that are referred to in drug and alcohol work:

depressants: drugs that depress or slow down the CNS (eg slow down
or decrease heart rate, reaction time, breathing)

stimulants: drugs that stimulate and speed up the CNS (eg increase and
speed up thinking and talking, and decrease the need for sleep)

hallucinogens: drugs that distort the CNS (eg ‘hearing’ colours, seeing
things which are not there, believing things to be true which are not).
Drug effects will vary. For example, although alcohol is a depressant drug
and will, depending upon the amount taken, slow the person down, the
initial effects may make the person feel a bit ‘high’ and relaxed.
Drugs that speed up the activity of the CNS (stimulants) include drugs such
as speed, cocaine and caffeine. Drugs that slow down the CNS activity
(depressants) include alcohol and heroin; while drugs that distort the CNS
(hallucinogens) include LSD and magic mushrooms.
Activity 5: Drug groups
In the table below, identify some of the major drugs that are commonly used and talked
about within the AOD area.
Depressants
(slow down the CNS)
Stimulants
(speed up the CNS)
Hallucinogens
(distort the CNS)
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Feedback 5
Depressants
Stimulants
Hallucinogens
Alcohol
Tobacco
LSD
Minor tranquillisers
(benzodiazepines)
Caffeine
Magic mushrooms
Coffee
Cannabis (in high doses)
Amphetamines
Ecstasy (in high doses)
Major tranquillisers
Opioids (narcotic analgesics):
Opium
Speed
Dexamphetamine
Heroin
Cocaine
Morphine
MDMA (Ecstasy)
Pethidine
Methadone
Codeine
Cannabis
Inhalants and solvents:
Petrol
Glue
Butane gas
Aerosols
Note: cannabis, though classified as a depressant, is also referred to and
grouped as a stimulant in some drug classification systems.
We now know that there are three main groupings of psychoactive drugs, so
classified due to their effects on the CNS. Next we’ll look at how individual
drugs are named and classified.
How are drugs named?
Activity 6: How are drugs named?
Take some time to think about some drugs that you know or have heard of. How are they
named? Do any of them have more than one name? Write down any ideas you may have on
this.
_________________________________________________________________________
_________________________________________________________________________
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Feedback 6
Drugs can be named in a variety of ways:

chemical name: a verbal blueprint of the drug’s structure

chemical group name: the similar chemical structure of a number of
drugs that come together as a ‘group’. An example of this is the group
of drugs called benzodiazepines. This group of drugs are all similar in
the way they are composed chemically and in the way that they work.

generic name: the general name that is used in the industry for a
particular drug. An example would be from the group of drugs called
benzodiazepines: diazepam and nitrazepam.

proprietary name: the brand or trade name that is given by the
manufacturer. You may be familiar with Valium or Serepax, which are
company brand or trade names.

general use name: how the drug is used or its general purpose (eg
Serepax, if used during the day as prescribed by a doctor, may be for
anxiety; if prescribed to be used at night, it may be to assist with sleep)

street name: the name by which the drug is referred to on the street. In
the example of Serepax, the street name might be ‘serries’.
An example of forms of a drug’s name:
Chemical name:
7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one
Chemical group name:
benzodiazepine
Generic name:
Diazepam
Proprietary name:
Valium
Generic use name:
Sleeping pills
Street name:
Pills
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There are many important reasons why we need to become familiar with the
different ways in which drugs are named or referred to. A scientist may refer
to a drug by the chemical name. A pharmacist and GP may use the chemical
group name, generic or the proprietary name of a drug. People unfamiliar
with pharmacology may refer to drugs by the specific use they have (eg
sleeping tablet, pain medication). The street name for drugs may be used by
people who take a drug outside of its intended purpose or to use more subtle
language to refer to a drug (eg ‘hammer’ or ‘dope’ in place of ‘heroin’). It
can be a little confusing, as different words can sometimes refer to the same
drug. In the AOD sector it is especially important for workers to be aware of
‘street’ names.
How are individual drugs classified?
There are three ways that drugs are classified:

therapeutic

legal

behavioural.
Therapeutic classification of drugs
This system classifies drugs according to the purpose or context in which
the drug is used or prescribed. One drug may have several therapeutic uses
at the same time or at different times. We usually identify the main
therapeutic classification according to the intention of the user.
Some examples:
14

Pethidine is used in hospitals for pain relief, while an individual might
use pethidine to ‘get out of it’. The first use would be classified as
analgesic use and the second would be classified as euphoric use
(feeling high).

Serepax may be prescribed to assist with sleep (hypnotic) for one person
and prescribed as a medication for anxiety for another (anti-anxiety).

Marijuana, if used to stimulate appetite and reduce nausea in people
undergoing chemotherapy for cancer, would be classified as an appetite
stimulant (in limited situations), but classified as an illicit substance by
someone using the drug for recreation or pleasure.

Morphine, given to a patient in hospital to relieve severe pain, is
classified as an analgesic. If used by someone with an opiate addiction,
it would be classified as a euphoriant (a drug that produces a feeling of
being ‘high’).
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Legal classification
You would probably be aware that drugs can be classified as legal and nonlegal (illicit), however, even amongst legal drugs there are different
classifications such as prescription and non prescription.
Some drugs are restricted by prescription, eg Serepax, and others are
restricted by social policy, eg alcohol and tobacco. The latter have age
restrictions, licensing restrictions, availability restrictions, advertising
restrictions and usage restrictions.
It is interesting to note that the legal/illegal classification system for drugs
has historically put more emphasis on who can and can’t access the drug as
opposed to the provision of pharmacological information about side effects
and toxicity.
Behavioural classification (effect on the CNS)
Drugs of the psychoactive type may cause people to behave in ways they
normally don’t when not under the influence. Alcohol may cause some
people to be less able to contain their anger or feelings for another person.
The behavioural classification system refers to the impact that psychoactive
drugs have at the level of the CNS. Drugs will cause some people to slow
down and others to speed upthe behaviour of the individual will depend
on many factors, including the amount taken, the quality of the drug, the
period over which the drug use has occurred and individual differences of
the person.
Now that we have considered the different ways of classifying drugs let’s
look at combing the three classification systems.
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Activity 7: Combined classification of drugs
Complete the following information about each drug.
1
Drug: heroin
Effect on the CNS:
_____________________________________________________________________
_____________________________________________________________________
Legal classification:
_____________________________________________________________________
_____________________________________________________________________
Therapeutic classification:
_____________________________________________________________________
_____________________________________________________________________
2
Drug: caffeine
Effect on the CNS:
_____________________________________________________________________
_____________________________________________________________________
Legal classification:
_____________________________________________________________________
_____________________________________________________________________
Therapeutic classification:
_____________________________________________________________________
_____________________________________________________________________
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Drug: cannabis
Effect on the CNS:
_____________________________________________________________________
_____________________________________________________________________
Legal classification:
_____________________________________________________________________
_____________________________________________________________________
Therapeutic classification:
_____________________________________________________________________
_____________________________________________________________________
4
Drug: nicotine
Effect on the CNS:
_____________________________________________________________________
_____________________________________________________________________
Legal classification:
_____________________________________________________________________
_____________________________________________________________________
Therapeutic classification:
_____________________________________________________________________
_____________________________________________________________________
5
Drug: ecstasy
Effect on the CNS:
_____________________________________________________________________
_____________________________________________________________________
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Legal classification:
_____________________________________________________________________
_____________________________________________________________________
Therapeutic classification:
_____________________________________________________________________
_____________________________________________________________________
Feedback 7
1
2
3
4
5
18
Drug: heroin
 Effect on the CNS: depressant.

Legal classification: illegal.

Therapeutic classification: a very good analgesic for terminal
illnesses, though not used in medicine in Australia since 1953.
Drug: caffeine
 Effect on the CNS: stimulant.

Legal classification: legal.

Therapeutic classification: possibly socially therapeutic.
Drug: cannabis
 Effect on the CNS: depressant.

Legal classification: illegal (but legal in limited situations).

Therapeutic classification: of value therapeutically for people
undergoing treatments for cancer or as an appetite stimulant for
some HIV/AIDS patients. Has therapeutic value for glaucoma
(pressure within the eye that can lead to blindness).
Drug: nicotine
 Effect on the CNS: Stimulant.

Legal classification: Legal.

Therapeutic classification: No known current therapeutic value.
Drug: ecstasy
 Effect on the CNS: Stimulant.

Legal classification: Illegal.

Therapeutic classification: No known current therapeutic value.
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Common terms relating to the action
of drugs
There are a number of terms that refer specifically to the actions of drugs.
Some of them you may have heard of and be familiar with; others may be
new to you. These terms are sometimes used interchangeably or even
incorrectly. Let’s take a closer look at them.
Dose
The dose of a drug is the amount of the drug that is taken at a particular
point in time. This is quite straightforward (eg two tablets three times a day
or 10 ml of cough medicine every four to six hours).
Overdose
Any dose of a drug in excess of the therapeutic or tolerant dose.
Half-life
Pharmacologically, the time required for half the amount of a drug in the
body to be eliminated or converted to another substance.
Dependence
When referring to drugs, this term may relate to either physical or
psychological dependence or both.
A person is said to be physically dependent on a drug when the body
requires more of the drug to achieve the drug effect that was previously
achieved with smaller doses of the drug. It is a state in which the body has
adjusted to the presence of a drug, so that when the drug is withdrawn, there
are clear physical signs of withdrawal usually involving discomfort and
pain.
Psychological dependence is a state that is characterised by emotional and
mental preoccupation with the drug’s effects and by a persistent craving for
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the drug. Some people may use a drug to reduce a mental craving without
developing a physical addiction.
The term dependence is often misused as relating to something unhealthy
when it is used in the context of drug use. Dependence is something that we
all have in common; we are all dependent on a number of things to keep us
safe and healthy. Dependence, in its broadest sense, is to be reliant upon,
having confidence in, trusting, depending on aid, support and so on.
There is a closer relationship between dependence and independence. The
aim within a healthy relationship is to get to a point of interdependence
where there is a healthy balance between the positions of dependence and
independence. In contrast, over-dependence (addiction) and overindependence (isolation) are both psychologically unhealthy states.
Figure 3: The dependence grid
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Activity 8: Drug dependence: case studies
1
Jodie has been having a lot of relationship problems and has been smoking cannabis
on the nights when she feels really low. Whenever she feels stressed, she really feels a
strong desire to have a smoke. What do you think is happening here in terms of
dependence?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2
Tom has been using a combination of drugs over the past six months that includes
heroin once or twice a day by snorting; marijuana two or three cones a week; and
ecstasy every weekend. Tom says that he can’t go out and socialise unless he is high
on something. What do you think is happening here in terms of dependence?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
Feedback 8
1
Jodie wants to use the drug to make her feel more psychologically
comfortable and feels that it will help her to push the painful feelings
away. In this example, Jodie appears to be psychologically dependent.
2
Tom is using heroin on a regular daily basis and his body has adjusted
to the drug. This will most likely see him having to use more and more
of the drug to achieve the same effect. Tom is physically and
psychologically dependent on heroin. The marijuana and ecstasy appear
to be more recreational but Tom feels that he can’t function in terms of
seeing his friends and partying unless he is using them. He is
psychologically dependent on these two drugs.
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Withdrawal
Withdrawal is the combination of physical and psychological symptoms that
are experienced by a person with a drug addiction when they abruptly stop
taking the drug. For a physical withdrawal to be experienced, a physical
dependence has to be present. If a person is experiencing a withdrawal
from an addictive substance, they are considered to be physically and
psychologically dependent/addicted, and have developed a tolerance to that
drug.
Are you clear about the link between a withdrawal syndrome and that of
physical dependence? If a drug user were to stop using heroin after three
months of heavy or continuous use the person would start experiencing
physical withdrawal symptoms within 36 hours. Some of the withdrawal
symptoms would include aches and pain in the extremities and back,
difficulty to relax and sleep, nausea and vomiting, flu like symptoms and so
on.
Tolerance
This term is linked to physical dependence and is often used
interchangeably. Tolerance to a drug occurs when a person is taking a
psychoactive drug such as heroin or alcohol on a regular daily basis. The
body attempts to adapt to the drug with the result that more of the drug is
required to achieve the same drug effect. Tolerance will develop more
quickly to a drug if the dosage is more frequent.
For example, a person in the first month of taking heroin might start with a
$30 hit once to twice per day. After the first month, the effect of the drug
will not be the same as it was when the person first started using. By the end
of that first month, this person’s body will become used to the heroin.
In other words, the CNS will slowly adjust to the heroin. To get the same
effect that was experienced in week one, the person will need to increase the
amount that they use.
Another example: someone aged 25 years might be regularly consuming
four to six schooners of beer on weekends. By the time they are 30 years old
they will have needed to increase this amount to get the same effect. They
might also increase the number of drinking sessions per week as the CNS
continues to adjust to previous levels of consumption.
The effect is that, over time, more and more of the drug will be consumed.
In the event that the intake of the drug remains constant and does not slowly
increase, the experience of the person using the drug will be that of
preventing withdrawal from occurring. Very little euphoric effect will be
experienced.
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Cross-tolerance
Cross-tolerance is a condition of a reduced tolerance to a drug due to the
acquired tolerance to another drug which produces similar effects (that is,
from the same drug group).
Where a person is tolerant to a drug such as heroin, they are tolerant to all
other drugs in the opiate group. In the event that the drug user is unable to
obtain and use heroin, they could use other opiate drugs that would provide
similar effects, depending on the dose used. There are a number of drugs
that share a cross-tolerance, including the narcotic analgesics (morphine,
methadone, opium, pethidine, codeine) and benzodiazepines and alcohol
which have a partial cross-tolerance.
Addiction
Addiction, dependence, and tolerance are all similar terms for the purposes
of understanding the basic effects of drugs on the CNS (although historically
and culturally the terms ‘addiction’ and ‘dependence’ have different
meanings and origins).
Addiction refers to a state of being addicted to some practice, habit or
substance.
The characteristics of addiction:

It diminishes awareness (that is, the drug becomes the central focus in
the life of the drug user in that it may numb the person mentally,
physically and spiritually).

It limits and detracts from other involvements (that is, all other
activities in the life of the drug user may take second place).

It lowers self-esteem.

It is not pleasurable.

It is predictable, repetitive and inflexible.
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Polydrug use
When people take drugs they often take more than one drug at a time. When
a person has consumed two or more drugs it is termed ‘polydrug use’. Poly
drug use may occur as simultaneous use (when drugs may be taken together,
often to get a heightened effect) or sequentially (one after the other to get a
longer lasting effect).
Drug interactions
There are a number of concepts we need to consider when we look at drug
interactions—how drugs interact with each other. The three key ideas to
focus on when we discuss interactions are:

addition

antagonism

potentiation.
Addition
Addition is where two different drugs combine to produce an intensified
response which is greater than the sum total of their two effects—such as
taking alcohol and using antihistamines, which is why this is not
recommended.
Antagonism
This occurs when drugs combine so that the second drug will lessen the
effect of the first drug. A good example of this is when a person takes heroin
(an opoid) overdoses and is given Narcan (an opiate antagonist) which
reverses the effect of the heroin.
Potentiation
This is where two drugs combine to produce an effect that is greater than the
sum of the two drugs. Two drugs that produce potentiation are alcohol and
diazepam.
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3256: Resource Book 2:1 Apply basic knowledge of pharmacology (Community services)
LO: 2003_136_004  OTEN, 2004/044/003/04/2004
Activity 9: Drug interactions scenario
Consider this scenario: After work, Jenny usually stops at the pub to have a few drinks with
her friends. Over the past week, due to some personal problems, her GP has prescribed her
Valium which she takes three times a day. After a few drinks, Jenny feels quite drunk and
light-headed, even though she has only had two drinks.
What do you think is occurring, in terms of the type of drug interaction Jenny experiences?
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Feedback 9
Jenny feels drunk due to the additive effect of the two drugs. When taking
drugs in combination, the effect of the alcohol combines with the effect of
Valium. This additive effect is also known as a synergistic effect. The
additive effect of a drug is also referred to as potentiation.
Where does interaction happen?
Interaction can happen in a number of different ways:

It may occur before the drug is taken—some drugs react chemically to
light or to the surfaces they are stored in (glass or plastic).

It may occur in the gastro intestinal system or in the liver as the drug is
carried through the body.

It may also occur at receptor sites as the drug is absorbed.

It could occur in the plasma (a constituent of blood).

It could occur as it is being eliminated (through the kidneys, bowel, skin
or lungs).
The site of interaction will depend on the drugs involved and the
individual’s own response, which as we have already identified can depend
on a whole range of factors, both physical and psychological.
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Summary
In this topic you have been introduced to the principles of pharmacology and
how this can apply to working with clients. We have looked at a range of
ideas, including a discussion of psychoactive drugs and their actions on the
central nervous system (CNS); the classification of drugs; and finally we
explored a range of definitions that you need to understand to work with
clients who have AOD problems.
Check your progress
You should now be able to understand the basic principles of pharmacology. Can you
answer the following questions confidently?
1
What is a drug?
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2
What is pharmacology?
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3
By what processes do psychoactive drugs act on the body? Which parts of the body are
involved in these processes?
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_____________________________________________________________________
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3256: Resource Book 2:1 Apply basic knowledge of pharmacology (Community services)
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4
What are the three main groupings of psychoactive drugs and what are their actions?
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5
How are different drugs named and classified?
_____________________________________________________________________
_____________________________________________________________________
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6
What are the common terms relating to the actions of drugs?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
Feedback: Check your progress
Go back through this topic to check your answers to these questions.
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Additional resources
Books
Commonwealth Department of Human Services and Health (1994)
Handbook for Medical Practitioners and Other Health Care Workers o
Alcohol and Other Drug Problems, AGPS, Canberra
Jacobs M and Fehr K (1998) Drugs and Drug Abuse, Addiction Research
Foundation, Toronto, Canada
Julien R M (1995) A Primer of Drug Action, Freeman & Co, San Francisco
Krivanek J (1988) Addictions, Allen & Unwin, Sydney
Mattick R P and Jarvis T J (eds) (1993) An Outline for the Management of
Alcohol Problems, NDARC, Sydney
Mattick R P and Hall W (eds) (1993) An Outline for the Management of
Opoid Dependency, NDARC, Sydney
Using the Internet
MIMS online at: http://www.mims.hcn.net.au
Australian Drug Information Network at: http://www.adin.com.au
Reach Out at: http://www.reeachout.com.au
Life Education Australia at: http://www.drugsafe.org
Australian Drug Foundation at: http://www.druginfo.adf.org.au
Family Drug Support at: http://www.fds.org.au
Aboriginal Drug and Alcohol Council (SA) Inc. at: http://www.adac.org.au
At the following link to this website is an Aboriginal story that looks at the
effects of petrol sniffing on the brain. It is simply but powerfully done and
explores the concept from an Aboriginal perspective:
http://www.adac.org.au/source/brainstory
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3256: Resource Book 2:1 Apply basic knowledge of pharmacology (Community services)
LO: 2003_136_004  OTEN, 2004/044/003/04/2004