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P A R T 4  Drugs acting on the central and peripheral nervous systems

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.

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

Presynaptic neuron

Tyramine (from diet)

Tyramine hydroxylase Dopa decarboxylase

Dopa

AP

Dopamine

Lithium

Nerve terminal

dopamine noradren- aline stores- blocks release of dopamine, noradrenaline decreases second messenger

MAO

Noradrenaline

responses Reuptake

Synaptic cleft

Ca+

Return to presynaptic cell

Inactive product to blood vessel

COMT

Into blood vessel

Adrenergic receptor α β 1 or β 2

Dopamine receptor: Antipsychotics block dopamine receptors

cAMP

Neuron or effector cell

FIGURE 22.1  Sites of action of the drugs used to treat mental disorders: antipsychotics, central nervous system stimulants, lithium.