336
P A R T 4
Drugs acting on the central and peripheral nervous systems
the reticular activating system (RAS) or problems with
response to that stimulation.
Attention-deficit disorders
involve various condi-
tions characterised by an inability to concentrate on
one activity for longer than a few minutes and a state of
hyperkinesis. These conditions are usually diagnosed in
school-aged children but can occur in adults.
ANTIPSYCHOTIC/NEUROLEPTIC DRUGS
The
antipsychotic
drugs, which are essentially dopamine-
receptor blockers, are used to treat disorders that
involve thought processes. Because of their associated
neurological adverse effects, these medications are also
called
neuroleptic
agents. At one time, these drugs were
known as
major tranquillisers
. However, that name
is no longer used because the primary action of these
drugs is not sedation but a change in neuron stimulation
and response (Figure 22.1).
Antipsychotics are classified as either typical or
atypical: Typical antipsychotics include chlorproma-
zine (
Largactil
), fluphenazine (
Modecate
), haloperidol
(
Serenace
), pericyazine (
Neulactil
), prochlorperazine
(
Stemetil
), trifluoperazine (
Stelazine
) and zuclopenthixol
(
Clopixol
). Atypical antipsychotics include amisulpride
(
Solian
), aripiprazole (
Abilify
), clozapine (
Clozaril
),
olanzapine (
Lanzek,
Zyprexa
), paliperidone (
Invega
),
quetiapine (
Delucon, Seroquel
), risperidone (
Ozidal,
Risperdal
) and ziprasidone (
Zeldox
). Table 22.1 lists
both typical and atypical antipsychotic agents, includ-
ing the specific type and the occurrence of sedation and
other adverse effects.
dopamine noradren-
aline stores- blocks
release of dopamine,
noradrenaline decreases
second messenger
responses
Reuptake
Nerve
terminal
Presynaptic
neuron
Synaptic
cleft
Neuron or
effector cell
Inactive product
to blood vessel
COMT
AP
Into blood vessel
Return to presynaptic cell
Ca+
Dopa
Tyramine (from diet)
Tyramine hydroxylase
Dopa decarboxylase
Lithium
Dopamine
MAO
Adrenergic
receptor
α β
1
or
β
2
cAMP
Noradrenaline
Dopamine receptor:
Antipsychotics block
dopamine receptors
FIGURE 22.1
Sites of action of the drugs used to
treat mental disorders: antipsychotics, central
nervous system stimulants, lithium.
