Pimozide
Pimozide is a diphenylbutylpiperidine antipsychotic specifically indicated for the suppression of motor and phonic tics in patients with Tourette’s disorder who have failed to respond adequately to standard treatment. It is reserved for severe cases due to its significant side effect profile and potential for serious cardiac complications.
Clinical Overview
Primary Clinical Applications
Pimozide is indicated exclusively for Tourette’s disorder in patients with severe symptoms who cannot take or have not responded to other medications. It is not approved for other psychotic conditions and should only be used when the potential benefits clearly outweigh the substantial risks.
Mechanism and Clinical Considerations
As a potent dopamine receptor antagonist, pimozide effectively suppresses tics but carries significant risks including QT prolongation, extrapyramidal symptoms, and tardive dyskinesia. The medication requires careful cardiac monitoring and should be used at the lowest effective dose.
Specialized Usage Requirements
Due to its narrow therapeutic indication and significant risk profile, pimozide requires specialized monitoring including baseline and periodic ECGs, and should only be prescribed by clinicians experienced in treating Tourette’s disorder.
Key Clinical Points
Boxed warning for QT prolongation and sudden death
Baseline and periodic ECGs are required, not advisory. Contraindicated in any history of cardiac arrhythmia or congenital long QT syndrome.
Tourette's disorder only, and second-line
Indicated solely for motor and phonic tics in patients who have failed standard treatment. It is not approved for schizophrenia or any other psychotic condition.
Electrolytes drive the cardiac risk
Hypokalaemia and hypomagnesaemia both amplify QT prolongation and should be corrected and monitored throughout treatment.
CYP3A4 inhibitors raise levels dangerously
Given the narrow cardiac safety margin, any strong inhibitor materially increases risk. Concurrent QT-prolonging drugs including quinidine, procainamide, and amiodarone are contraindicated.
Weight-based paediatric dosing from age 12
Starting at 0.05 mg/kg at bedtime, capped at 0.2 mg/kg or 10 mg daily, whichever is lower. Not recommended below 12 years.
Prescribing Information
Dosing & Administration
Tourette’s Disorder:
- Initial: 0.05 mg/kg preferably at bedtime (or 1-2 mg daily)
- Titration: Increase every other day as needed
- Maximum: 0.2 mg/kg/day or 10 mg/day (whichever is less)
Pediatric (>12 years):
- Same dosing as adults
- Children <12 years: Not recommended
Indications
- Tourette’s disorder (motor and phonic tics)
- Reserved for severe cases unresponsive to standard treatment
Contraindications
- History of cardiac arrhythmias
- Congenital long QT syndrome
- Concurrent use of drugs that prolong QT interval
- Severe CNS depression
- Comatose states
- History of severe toxic CNS depression
Warnings & Precautions
- Boxed Warning: QT prolongation and risk of sudden death
- Cardiac monitoring: Baseline and periodic ECGs required
- Tardive dyskinesia: Risk increases with duration of treatment
- Neuroleptic malignant syndrome: Rare but potentially fatal
- Electrolyte monitoring: Hypokalemia and hypomagnesemia increase QT risk
Drug Interactions
- QT-prolonging drugs: Contraindicated (quinidine, procainamide, amiodarone)
- CYP3A4 inhibitors: Increase pimozide levels
- CNS depressants: Enhanced sedation
- Phenothiazines: Additive anticholinergic effects
Adverse Reactions
Common:
- Extrapyramidal symptoms, sedation, anticholinergic effects
Serious:
- QT prolongation, cardiac arrhythmias, tardive dyskinesia
Special Populations
- Pediatric: Not recommended under 12 years
- Elderly: Increased sensitivity to adverse effects
- Hepatic/Renal Impairment: Use with extreme caution
- Pregnancy: Category C – use only if clearly needed
Frequently Asked Questions
What is Pimozide used for?
Pimozide is a diphenylbutylpiperidine antipsychotic specifically indicated for the suppression of motor and phonic tics in patients with Tourette’s disorder who have failed to respond adequately to standard treatment. It is reserved for severe cases due to its significant side effect profile and potential for serious cardiac complications.
What class of drug is Pimozide?
Pimozide is classified as: Typical (First-Generation) Antipsychotic.
Boxed warning for QT prolongation and sudden death?
Baseline and periodic ECGs are required, not advisory. Contraindicated in any history of cardiac arrhythmia or congenital long QT syndrome.
Tourette's disorder only, and second-line?
Indicated solely for motor and phonic tics in patients who have failed standard treatment. It is not approved for schizophrenia or any other psychotic condition.
Electrolytes drive the cardiac risk?
Hypokalaemia and hypomagnesaemia both amplify QT prolongation and should be corrected and monitored throughout treatment.
CYP3A4 inhibitors raise levels dangerously?
Given the narrow cardiac safety margin, any strong inhibitor materially increases risk. Concurrent QT-prolonging drugs including quinidine, procainamide, and amiodarone are contraindicated.
Source: FDA prescribing information (DailyMed)