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Atypical Antipsychotic — Selective 5-HT2A Inverse Agonist (Parkinson's Disease Psychosis) Pregnancy: There are no data on use in pregnant women that would allow assessment of the drug-associated risk of major congenital malformations or miscarriage. In animal reproduction studies no adverse developmental effects were seen when pimavanserin was given orally to rats or rabbits during organogenesis at doses up to 10- or 12-times the maximum recommended human dose of 34 mg/day; administration to pregnant rats during pregnancy and lactation resulted in maternal toxicity and lower pup survival and body weight at doses 2-times the maximum recommended human dose. (US labelling; no UK SPC available in the source bundle.)

Pimavanserin

Brand names: Nuplazid

Pimavanserin is an atypical antipsychotic agent used in the treatment of hallucinations and delusions associated with Parkinson's disease psychosis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 34 mg once daily, without titration
Route: Oral
Frequency: Once daily
Max: 34 mg once daily is the recommended dose; no higher dose is stated in the label. Reduce to 10 mg once daily when co-administered with a strong CYP3A4 inhibitor
SOURCE CAVEAT — NO UK SPC: the source bundle contains no eMC record for pimavanserin, so this dose is taken from the US FDA prescribing information for NUPLAZID (Acadia Pharmaceuticals, label date 2026-06-18, https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2199d74b-37ed-408c-97af-ef036899216b), §2.1. US labelling may differ from UK practice and pimavanserin may not hold a UK marketing authorisation — the clinician must verify licensing status and dose against current UK prescribing references before this is published. INDICATION on the US label: hallucinations and delusions associated with Parkinson's disease psychosis (the label carries a boxed warning on increased mortality in elderly patients with dementia-related psychosis, and states NUPLAZID is not approved for treating patients with dementia who experience psychosis unless their hallucinations and delusions are related to Parkinson's disease). ADMINISTRATION: can be taken with or without food; capsules can be taken whole, or opened and the entire contents sprinkled over a tablespoon (15 mL) of applesauce, yogurt, pudding or a liquid nutritional supplement — consume the drug/food mixture immediately without chewing and do not store for future use. DOSAGE MODIFICATION FOR CYP3A4 INHIBITORS: with strong CYP3A4 inhibitors the recommended dose is 10 mg taken orally as one tablet once daily. CYP3A4 INDUCERS: avoid concomitant use of strong or moderate CYP3A4 inducers. GERIATRIC: no dose adjustment is required for elderly patients. PAEDIATRIC: safety and effectiveness in paediatric patients have not been established — no paediatric dose is stated and none should be inferred; verify any under-18 use against a children's formulary. No renal impairment guidance was present in the sections retrieved — verify. Several label sections were truncated at the source-fetch limit.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • History of a hypersensitivity reaction to pimavanserin or any of its components — rash, urticaria and reactions consistent with angioedema (e.g. tongue swelling, circumoral oedema, throat tightness and dyspnoea) have been reported

Side effects

  • Most common adverse reactions (incidence >= 5% and twice the rate of placebo): peripheral oedema and confusional state
  • QT interval prolongation
  • Increased all-cause mortality in elderly patients with dementia-related psychosis (boxed warning; antipsychotic class effect)
  • Hypersensitivity reactions: rash, urticaria and reactions consistent with angioedema (tongue swelling, circumoral oedema, throat tightness, dyspnoea) — reported post-marketing

Interactions

  • Drugs that prolong the QT interval (e.g. Class 1A antiarrhythmics, Class 3 antiarrhythmics, certain antipsychotics or antibiotics) — avoid concomitant use, as the QT effects may be additive and increase the risk of cardiac arrhythmia
  • Strong CYP3A4 inhibitors — increase pimavanserin exposure; reduce the dose to 10 mg once daily
  • Strong or moderate CYP3A4 inducers — reduce pimavanserin exposure; avoid concomitant use

Clinical monograph

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.

Reference: Ballard et al. Lancet 2021 (HARMONY trial); MHRA SPC Nuplazid; Cummings et al. Lancet 2014 (Phase III PDP trial); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.