Antipsychotics





Introduction

Antipsychotics act as dopamine D2 receptor antagonists, blocking dopaminergic transmission in the mesolimbic pathways. Conventional antipsychotics are associated with problematic extrapyramidal side-effects which has led to the development of atypical antipsychotics such as clozapine

Adverse effects

Extrapyramidal side-effects
  • Parkinsonism
  • Acute dystonia: sustained muscle contraction (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)

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: galactorrhoea, impaired glucose tolerance
  • Neuroleptic malignant syndrome: pyrexia, muscle stiffness
  • Reduced seizure threshold (greater with atypicals)
  • Prolonged QT interval (particularly haloperidol)