pimozide: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
pimozide: clinical details
Prescribing considerations
- Review cardiac history, family history of long-QT syndrome or sudden unexplained cardiac death, interacting medicines and factors causing electrolyte loss.
- Assess seizure history, hepatic or renal impairment, thromboembolism risk, dehydration or heat exposure, thyroid disease and phaeochromocytoma.
- Avoid abrupt withdrawal; recurrence of psychosis and withdrawal or movement symptoms may be delayed.
- The selected product is not licensed for dementia-related behavioural disturbance.
Contraindications and cautions
- Congenital or acquired long-QT syndrome, previous torsades de pointes, significant arrhythmia or bradycardia, uncorrected hypokalaemia or hypomagnesaemia, recent myocardial infarction, uncompensated heart failure or specified antiarrhythmic treatment.
- Severe central nervous system depression, hypersensitivity to pimozide or related derivatives, depression or Parkinson's syndrome.
- Concomitant QT-prolonging medicines, strong CYP3A4 or CYP2D6 inhibitors, and specified serotonin-reuptake inhibitors.
Monitoring
- Obtain an ECG before initiation and periodically during treatment; reassess promptly for palpitations, dizziness or syncope.
- Check and correct potassium and magnesium, with periodic electrolyte monitoring where clinically indicated.
- Monitor for extrapyramidal symptoms, tardive dyskinesia, neuroleptic malignant syndrome, seizures, prolactin-related effects and venous thromboembolism risk.
- Review ongoing need, response, adverse effects and the complete interaction profile regularly.
Clinical pharmacology
Pimozide is an orally active central dopamine-receptor antagonist. It is metabolised mainly through CYP3A4 and to a lesser extent CYP2D6, has a long and highly variable elimination half-life, and can inhibit cardiac hERG channels, contributing to QT prolongation.
Formulation and product differences
- The selected product is a green, circular, biconvex oral tablet with a score line and can be divided into equal halves.
- It contains hydrogenated cottonseed oil and colourants E172 and E132; check the full excipient list when allergy or intolerance is relevant.
pimozide preparations and strengths
Tablet
Route: Oral
Strengths: 4 mg
pimozide interactions
Pimozide has numerous clinically important interactions. Check all prescribed, over-the-counter and herbal products before treatment or any medicine change.
QT-prolonging medicines
Antiarrhythmics, some antidepressants, antipsychotics, antihistamines and antimalarials can add to the risk of dangerous heart rhythms and are contraindicated where specified.
Strong CYP3A4 inhibitors
Azole antifungals, macrolide antibiotics, protease inhibitors and nefazodone can markedly raise pimozide exposure and are contraindicated.
CYP2D6 inhibitors
Medicines such as quinidine can raise pimozide concentrations and increase QT-prolongation risk; concomitant use is contraindicated.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.