Antipsychotics

Antipsychotics are a group of drugs used in the management of schizophrenia and other forms of psychosis, mania and agitation. They are usually divided into typical and atypical antipsychotics. The atypical antipsychotics were developed due to the problematic extrapyramidal side-effects which are associated with the first generation of typical antipsychotics.

	Typical antipsychotics	Atypical antipsychotics
Mechanism of action	Dopamine D2 receptor antagonists, blocking dopaminergic transmission in the mesolimbic pathways	Act on a variety of receptors (D2, D3, D4, 5-HT)
Adverse effects	Extrapyramidal side-effects and hyperprolactinaemia common	Extrapyramidal side-effects and hyperprolactinaemia less common
Metabolic effects
Examples	Haloperidol
Chlorpromazine	Clozapine
Risperidone
Olanzapine

The rest of this section will focus on typical antipsychotics, with atypical antipsychotics covered elsewhere.

Extrapyramidal side-effects (EPSEs)

Parkinsonism
acute dystonia
- sustained muscle contraction (e.g. torticollis, oculogyric crisis)
- may be managed with procyclidine
akathisia (severe restlessness)
tardive dyskinesia (late onset of choreoathetoid movements, abnormal, involuntary, may occur in 40% of patients, may be irreversible, most common is chewing and pouting of jaw)

The Medicines and Healthcare products Regulatory Agency has issued specific warnings when antipsychotics are used in elderly patients:

increased risk of stroke
increased risk of venous thromboembolism

Other side-effects

antimuscarinic: dry mouth, blurred vision, urinary retention, constipation
sedation, weight gain
raised prolactin
- may result in galactorrhoea
- due to inhibition of the dopaminergic tuberoinfundibular pathway
impaired glucose tolerance