Home Drug Guide Pimozide

Drug Guide

Generic Name

Pimozide

Brand Names Orap

Classification

Therapeutic: Antipsychotic (Neuroleptic)

Pharmacological: Diphenylbutylpiperidine class dopamine antagonist

FDA Approved Indications

Tourette's disorder (selected cases)

Mechanism of Action

Pimozide is a dopamine receptor antagonist, primarily blocking D2 dopaminergic receptors in the central nervous system, which helps reduce tics in Tourette's disorder.

Dosage and Administration

Adult: Initially 2 mg twice daily, titrated up slowly based on response and tolerability; typical dose range: 4-10 mg/day.

Pediatric: Use is limited; if prescribed, dosing must be cautious and closely monitored, typically starting at low doses under expert supervision.

Geriatric: Dose reduction recommended due to increased susceptibility to adverse effects.

Renal Impairment: Use with caution; no specific adjustments; monitor closely.

Hepatic Impairment: Use with caution; hepatic function should be monitored and dose adjusted accordingly.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Extensively distributed in body tissues; crosses the blood-brain barrier.

Metabolism: Primarily hepatic via CYP3A4 enzyme.

Excretion: Excreted mainly in the feces and urine.

Half Life: Approximately 54 hours, allowing once-daily dosing in some cases.

Contraindications

Known hypersensitivity to pimozide or other phenylpiperidines.
Comorbid Long QT syndrome or other significant cardiac arrhythmias.
Concurrent use with other drugs that prolong QT interval.

Precautions

Use with caution in patients with cardiovascular disease, electrolyte disturbances, or a history of seizures.
Monitor for neuroleptic malignant syndrome, tardive dyskinesia, and other extrapyramidal symptoms.
Pregnancy and lactation: consider risks versus benefits; consult detailed guidelines.

Adverse Reactions - Common

Sedation (Common)
Dry mouth (Common)
Dizziness (Common)
Constipation (Common)
Weight gain (Common)

Adverse Reactions - Serious

QT prolongation / Torsades de Pointes (Serious, potentially life-threatening)
Neuroleptic malignant syndrome (NMS) (Rare)
Extrapyramidal symptoms (Less common but possible)
Seizures (Rare)

Drug-Drug Interactions

Other QT prolonging drugs (e.g., certain antiarrhythmics, antibiotics, antidepressants).
CYP3A4 inhibitors (which may increase pimozide levels).
CNS depressants.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor cardiac status (ECG) before and during treatment, especially QT interval. Observe for symptoms of extrapyramidal symptoms, NMS, and neuropsychiatric changes.

Diagnoses:

Risk of falls due to sedation or orthostatic hypotension.
Risk of cardiac arrhythmias.

Implementation: Administer with food to reduce GI upset. Educate patient on avoiding other QT prolonging agents.

Evaluation: Assess effectiveness in reducing tics and monitor for adverse effects.

Patient/Family Teaching

Do not operate machinery or drive until stable.
Report any signs of irregular heartbeat, fainting, or seizures.
Avoid alcohol and other CNS depressants.
Inform about possible side effects and when to seek medical attention.

Special Considerations

Black Box Warnings:

QT prolongation and risk of sudden death.
Elderly patients with dementia-related psychosis treated with antipsychotics are at increased risk of death.

Genetic Factors: Genetic polymorphisms in CYP3A4 may affect metabolism.

Lab Test Interference: None specified.

Overdose Management

Signs/Symptoms: Severe sedation, hypotension, QT prolongation, seizures, cardiac arrhythmias.

Treatment: Supportive care; manage arrhythmias; activated charcoal if ingestion is recent; administer intravenous magnesium if QT prolongation occurs; vagal maneuvers or medications for arrhythmias as needed.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable for up to 24 months if properly stored.