304
P A R T 4
Drugs acting on the central and peripheral nervous systems
T
he drugs discussed in this chapter are used to alter an
individual’s responses to environmental stimuli. They
have been called
anxiolytics
because they can prevent
feelings of tension or fear;
sedatives
because they can
calm people and make them unaware of their environ-
ment;
hypnotics
because they can cause sleep; and minor
tranquillisers because they can produce a state of tran-
quillity in anxious individuals. In the past, a given drug
would simply be used at different doses to yield each of
these effects. Further research into how the brain reacts
to outside stimuli has resulted in the increased availabil-
ity of specific agents that produce particular goals and
avoid unwanted adverse effects. Use of these drugs also
varies across the lifespan (Box 20.1).
STATES AFFECTED BY ANXIOLYTIC AND
HYPNOTIC DRUGS
Anxiety
Anxiety
is a feeling of tension, nervousness, apprehen-
sion or fear that usually involves unpleasant reactions to
a stimulus, whether actual or unknown. Anxiety is often
accompanied by signs and symptoms of the sympathetic
stress reaction (see Chapter 29), which may include
sweating, fast heart rate, rapid breathing and elevated
blood pressure. Mild anxiety, a not uncommon reaction,
may serve as a stimulus or motivator in some situations.
A person who feels anxious about being alone in a
poorly lit parking lot at night may be motivated to take
extra safety precautions. When anxiety becomes over-
whelming or severe, it can interfere with the activities
of daily living and lead to medical problems related to
chronic stimulation of the sympathetic nervous system.
A severely anxious person may, for example, be afraid
to leave the house or to interact with other people. In
these cases, treatment is warranted. Anxiolytic drugs
are drugs that are used to lyse or break the feeling of
anxiety.
Both severe and chronic anxiety are recognised
mental illnesses. Mental health is one of the Australian
government’s nine National Health Priority Areas; for
more information on mental health in Australia, see
.
Sedation
The loss of awareness and reaction to environmen-
tal stimuli is termed
sedation
. This condition may be
BOX 20.1
Drug therapy across the lifespan
Anxiolytic and hypnotic agents
CHILDREN
Use of anxiolytic and hypnotic drugs with children is
challenging.The response of the child to the drug may
be unpredictable; inappropriate aggressiveness, crying,
irritability and tearfulness are common.
Of the benzodiazepines, only clonazepam and diazepam
have established paediatric dosages. Some of the others
are used in paediatric settings, and dosage may be
calculated using age and weight.
The barbiturates, being older drugs, have established
paediatric dosages.These drugs must be used with caution
because of the often unexpected responses. Children
must be monitored very closely for CNS depression and
excitability.
Chloral hydrate is approved for use in children.The
potential for adverse effects and the unpleasant taste
and odour make the drug less desirable as a sleep agent.
The antihistamines diphenhydramine, trimeprazine and
promethazine are more popular for use in helping to calm
children and to induce rest and sleep. Care must be taken
to assess for possible dried secretions and effects on
breathing. Dosage must be calculated carefully.
ADULTS
Adults using these drugs for the treatment of insomnia
need to be cautioned that they are for short-term use
only.The reason for the insomnia should be sought
(e.g. medical, hormonal or anxiety problems). Other
methods for helping to induce sleep—established
routines, quiet activities before bed, a back-rub or warm
bath—should be encouraged before drugs are prescribed.
Adults receiving anxiolytics also may need referrals for
counselling and diagnosis of possible causes. Adults
should be advised to avoid driving and making legal
decisions when taking these drugs.
Liver function should be evaluated before and
periodically during therapy.
PREGNANCY AND BREASTFEEDING
These drugs are contraindicated during pregnancy
and breastfeeding because of the potential for adverse
effects on the fetus and possible sedation of the baby.
The antihistamines, which have not been associated with
congenital malformations, may be the safest to use, with
caution, if an anxiolytic or hypnotic drug must be used.
OLDER ADULTS
Older people may be more susceptible to the adverse
effects of these drugs, from unanticipated CNS effects to
increased sedation, dizziness, and even hallucinations.
Dosages of all of these drugs should be reduced and the
person should be monitored very closely for toxic effects
and to provide safety measures if CNS effects do occur.
Baseline liver and renal function tests should be
performed, and these values should be monitored
periodically for any changes that would indicate a need to
decrease dosage further or to stop the drug.
Non-drug measures to reduce anxiety and to help
induce sleep are important with older people.The person
should be screened for physical problems, neurological
deterioration, or depression, which could contribute to the
insomnia or anxiety.
