Antipsychotics

Antipsychotic medications may be classed as first or second generation.

First-generation (or conventional) antipsychotics act predominantly by blocking dopamine D2 receptors in the brain, blocking dopaminergic transmission in the mesolimbic pathways, but are associated with problematic extrapyramidal side-effects. The second-generation (or atypical) antipsychotic drugs act on a range of receptors in addition to the D2 receptors. In comparison to first-generation antipsychotic drugs they are generally associated with a lower risk for acute extrapyramidal symptoms and tardive dyskinesia.

Risks and side effects

First-generation (or conventional) antipsychotics are associated with problematic extrapyramidal side-effects and hyperprolactinaemia. Second-generation antipsychotic drugs are associated with weight gain, glucose intolerance and a range of other side effects.

Extrapyramidal side-effects

• Parkinsonism
• acute dystonia (e.g. torticollis, oculogyric crisis)
• 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)

Other side-effects

• antimuscarinic: dry mouth, blurred vision, urinary retention, constipation
• sedation, weight gain
• raised prolactin: galactorrhoea, impaired glucose tolerance
• neuroleptic malignant syndrome: pyrexia, muscle stiffness
• reduced seizure threshold (greater with atypicals)
• prolonged QT interval (particularly haloperidol)