Pimavanserin

How it works

It acts as a selective inverse agonist and antagonist at serotonin 5-HT2A receptors, with low affinity for dopamine receptors, which allows symptomatic benefit without worsening motor function.

Prescribing in practice

• It can prolong the QT interval, so avoid co-administration with other QT-prolonging drugs and use caution in patients with cardiac arrhythmia risk.
• As with all antipsychotics, use in elderly patients with dementia-related psychosis is associated with increased mortality.
• It is metabolised mainly by CYP3A4, so dose adjustment may be needed with strong CYP3A4 inhibitors or inducers.

Monitoring

Monitor the ECG where cardiac risk factors are present and review psychiatric and motor status regularly.

Counselling the patient

• It may take some weeks to see the full benefit on hallucinations and delusions.
• Tell your doctor about all other medicines you take, as some can affect your heart rhythm when combined with this drug.
• Do not stop the medicine suddenly without medical advice.

Evidence & guidelines

Pimavanserin's role in Parkinson's disease psychosis is supported by randomised controlled trial evidence and product licensing for this indication.