Antipsychotics can be classified by their structure but can also be distinguished by their pharmacology, their action at receptors, and by their clinical properties. Typical (also called conventional) antipsychotics act primarily at dopamine receptors. Atypical antipsychotics act on other receptors as well as dopamine, and are less likely than typical antipsychotics to cause movement disorders as a side effect. The following are atypical antipsychotics are licensed in the UK: amisulpiride (brand name Solian), aripiprazole (Abilify), clozapine (Clozaril), olanzapine (Zyprexa), quetiapine (Seroquel), risperidone (Risperdal) and zotepine (Zoleptil).
As with all effective medicines antipsychotics can produce side effect in some individuals. The most common side effects include movement disorders that may resemble Parkinson’s disease (referred to as extrapyramidal effects, anticholinergic effects such as dry mouth, feelings of dizziness or light headedness, constipation and blurred vision (so called as they are due to the action of these drugs on cholinergic receptors in the brain and body) and weight gain.
It is important to appreciate that this is not a comprehensive list of the possible side effects of antipsychotics. Full guidance on prescribing and use, including possible side effects, of antipsychotics is provided in the Summary of Product Characteristics (SPC) for health professionals and the patient information leaflet (PIL) that should accompany the medicine.
More recently concerns have arisen that patients receiving risperidone and olanzapine in dementia were at an increased risk of stroke compared with patients receiving placebo (dummy pill) and that the balance of risks and benefits was considered to be unfavourable in the dementia population. Atypical antipsychotics are not authorised for the treatment of dementia related psychosis and/or behaviour disturbances. Prescribers were informed of this risk and advised to review the treatment of all patients receiving atypical antipsychotics in dementia as the risk of stroke for other atypical antipsychotics could not be excluded: