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Pimozide

Pimozide is a typical antipsychotic medication of the diphenylbutylpiperidine class, primarily indicated for the suppression of severe motor and phonic tics in patients with Tourette's disorder who have not responded adequately to standard treatments such as haloperidol.^[1] Its chemical name is 3-[1-[4,4-bis(4-fluorophenyl)butyl]piperidin-4-yl]-1H-benzimidazol-2-one, with a molecular formula of C₂₈H₂₉F₂N₃O and a molecular weight of 461.5 g/mol.^[2] Administered orally as tablets, pimozide exerts its therapeutic effects by antagonizing dopamine D2 receptors in the brain, thereby reducing abnormal excitement and tic severity, though it does not cure the underlying condition.^[3]^[4] Approved by the U.S. Food and Drug Administration (FDA) under the brand name Orap, pimozide is available in 1 mg and 2 mg strengths and is typically initiated at low doses—such as 1-2 mg daily for adults or 0.05 mg/kg for children over 12 years—to minimize risks, with gradual titration up to a maximum of 10 mg per day based on clinical response and electrocardiogram (ECG) monitoring.^[1] It is metabolized primarily in the liver via cytochrome P450 enzymes (CYP3A4, CYP1A2, and CYP2D6), with a half-life of approximately 55 hours and peak plasma levels reached 6-8 hours after dosing.^[1] While its primary use is in Tourette's syndrome for patients aged 12 and older, pimozide has been studied off-label for conditions like schizophrenia maintenance therapy and delusional disorders, though it is not approved for behavioral problems in older adults with dementia due to increased mortality risk.^[3]^[5] Pimozide carries significant safety concerns, including the potential for QT interval prolongation, which can lead to serious arrhythmias or sudden death, necessitating baseline and periodic ECGs and avoidance of concurrent use with other QT-prolonging drugs or substances like grapefruit juice.^[4]^[1] Other notable risks include tardive dyskinesia, neuroleptic malignant syndrome, and extrapyramidal symptoms such as muscle stiffness and tremors, with common side effects encompassing dizziness, drowsiness, dry mouth, and blurred vision.^[3] Contraindications include congenital long QT syndrome, significant cardiac arrhythmias, and hypersensitivity to the drug, and it should be used cautiously in patients with hepatic or renal impairment.^[1]

Clinical Use

Indications

Pimozide is primarily indicated for the suppression of severe motor and phonic tics associated with Tourette's disorder in patients who have not responded adequately to standard treatments, such as other antipsychotics or alpha-2 agonists.^[6] In the United States, the FDA approves its use specifically for this purpose in individuals aged 12 years and older, reserving it for cases where tics significantly impair daily functioning due to its unfavorable risk-benefit profile compared to first-line therapies.^[6] Historically developed as an antipsychotic in the 1960s, pimozide received initial approvals for schizophrenia management in several countries, including parts of Europe where it remains authorized for chronic schizophrenia and related psychoses under strict monitoring.^[7] However, in the US, its broader application for schizophrenia has been curtailed owing to concerns over cardiac risks, particularly QT interval prolongation, while in parts of the EU it remains authorized for chronic schizophrenia and related psychoses under strict monitoring.^[6]^[7] Off-label applications include the treatment of delusional parasitosis, where case reports and small studies suggest partial or complete symptom resolution in some adults, though it lacks FDA approval and robust clinical trial support.^[8] Similarly, limited evidence from pilot studies indicates potential utility in combination with other agents for chorea in Huntington's disease, but this remains investigational without regulatory endorsement.^[9]

Dosage and Administration

Pimozide is administered orally in tablet form for the management of motor and phonic tics in patients with Tourette's syndrome, typically starting at low doses to minimize side effects such as extrapyramidal symptoms. The initial dose for adults is 1 to 2 mg per day, given in divided doses, while for children aged 12 years and older, it is 0.05 mg/kg per day, preferably administered once at bedtime.^[6]^[10] Dosage should be titrated slowly, increasing by 1 mg every other day in adults or every third day in children, based on clinical response and tolerability, to achieve the lowest effective dose that balances tic suppression with adverse effects.^[6]^[11] The maintenance dose is generally less than 0.2 mg/kg per day or 10 mg per day, whichever is lower, divided into one or two doses, with a maximum of 10 mg per day not to be exceeded.^[6]^[10] Tablets may be taken with or without food, and treatment is often long-term but requires periodic reassessment, including attempts to reduce the dose every 1 to 2 weeks to evaluate ongoing need.^[4]^[6] For patients with hepatic impairment, doses should be reduced and titrated cautiously due to potential increases in blood levels and risk of side effects; use pimozide with caution in patients with renal impairment due to potential increases in blood levels and risk of side effects.^[12]^[4] Pediatric use is restricted to those 12 years and older, with weight-based dosing as outlined.^[10] Discontinuation should be gradual, with slow tapering to prevent withdrawal symptoms such as exacerbation of tics, allowing 1 to 2 weeks between reductions to distinguish between rebound effects and underlying disease progression.^[6]^[10]

Efficacy and Safety

Efficacy Evidence

Pimozide received FDA approval in 1984 for the treatment of motor and phonic tics in Tourette's syndrome, based on evidence from two controlled clinical investigations involving patients aged 8 to 53 years.^[6] These included a 6-week placebo-controlled trial with 20 patients and a 24-week open-label extension in 36 children aged 2 to 12, demonstrating pimozide's ability to suppress tics compared to placebo.^[6] Double-blind trials from the 1980s, such as a crossover study of 20 patients, showed significant tic reductions with pimozide versus placebo, with mean tic severity scores improving from 4.42 to 1.52 on standardized scales (p=0.0001) and tic counts decreasing substantially in responsive cases.^[13] In pivotal trials, pimozide led to notable improvements in tic severity, as measured by scales like the Tourette Syndrome Severity Scale and, in later studies, the Yale Global Tic Severity Scale (YGTSS). For instance, a randomized double-blind crossover trial comparing pimozide to risperidone reported YGTSS total tic scores of 34.2 after pimozide treatment, indicating meaningful symptom reduction from baseline, though slightly less than with risperidone (25.2, p=0.05).^[14] Response rates in these early controlled studies ranged up to 81% for tic suppression, establishing pimozide as an effective option for moderate to severe cases.^[15] Comparative studies have shown pimozide to be superior to haloperidol in certain older trials for tic suppression, particularly in children and adolescents, where pimozide significantly outperformed placebo while haloperidol did not (p<0.05 for primary outcome).^[16] Additionally, pimozide was associated with fewer extrapyramidal symptoms and better cognitive performance, such as improved memory search efficiency, compared to haloperidol.^[17] In contrast, recent analyses, including a 2009 Cochrane review (updated 2012) of trials up to 2008, found no significant differences in efficacy between pimozide and atypical antipsychotics like risperidone for tic reduction.^[13] Long-term data from observational studies indicate sustained tic benefits with pimozide in a majority of patients, with 81% achieving good clinical response over extended periods at doses of 0.5–9 mg/day, and chronic use appearing more effective than short-term administration for maintaining tic control.^[15] However, discontinuation rates reached 20–30% in some cohorts due to emerging side effects, limiting its long-term applicability.^[13] Study limitations include small sample sizes (9–57 participants per trial) and a lack of large-scale randomized controlled trials after 2000, with most evidence derived from short-duration (up to 8 weeks) studies of fair methodological quality.^[13] There is no strong evidence supporting pimozide's efficacy for non-Tourette's uses, such as anxiety—where it offers no advantages over standard anxiolytics—or delusions, where results are mixed and often fail to confirm therapeutic benefits beyond placebo.^[18]^[19] As of 2025, the American Academy of Neurology's 2019 guidelines (with no major updates noted) recommend pimozide as a second- or third-line option for Tourette's tics, classifying it as possibly effective (standardized mean difference 0.66, 95% CI 0.06–1.25) with level C evidence, emphasizing the need for ECG monitoring due to QT prolongation risks.^[20]^[21]

Adverse Effects

Pimozide, a typical antipsychotic, is associated with a range of adverse effects, predominantly affecting the neurological and cardiovascular systems. Common effects, occurring in more than 10% of patients, include extrapyramidal symptoms (EPS) such as dystonia and akathisia, reported in up to 40% of participants in short-term clinical trials for Tourette's disorder.^[22] Sedation is also frequent, affecting 25% of children in a 24-week trial and up to 70% of adults in a smaller 6-week study.^[22] Weight gain is minimal with longer-term use (e.g., ~1 kg over 4 weeks in short-term trials), though pimozide generally causes less weight gain than many atypical antipsychotics.^[14] Serious adverse effects include QT interval prolongation, which is dose-dependent and increases the risk of torsades de pointes, a potentially fatal arrhythmia; this cardiac risk is rare at therapeutic doses but has been documented in post-marketing reports, particularly at doses exceeding 10 mg/day.^[22] Tardive dyskinesia, characterized by involuntary movements, carries a 5-10% risk with long-term use, consistent with typical antipsychotics, and may be irreversible in some cases.^[23] Other notable effects encompass hyperprolactinemia, leading to symptoms like galactorrhea or amenorrhea, with an incidence of approximately 80% in pediatric and adolescent populations based on endocrine monitoring studies.^[24] Mild anticholinergic effects, such as dry mouth, occur in about 25% of patients in clinical trials.^[22] Increased appetite has been noted in surveillance data.^[25] Risk factors for adverse effects include higher doses, female sex, electrolyte imbalances like hypokalemia or hypomagnesemia, and concurrent use of other QT-prolonging drugs; post-marketing surveillance highlights elevated cardiac risks in elderly patients and those with genetic variations in CYP2D6 metabolism.^[22]^[26] Management strategies involve dose reduction or antiparkinsonian agents for EPS, with baseline and periodic ECG monitoring recommended to mitigate cardiac risks; discontinuation is advised if QT prolongation exceeds 500 msec or serious arrhythmias occur.^[22]^[26]

Contraindications and Precautions

Contraindications

Pimozide is contraindicated in patients with congenital long QT syndrome due to the drug's potential to further prolong the QT interval and increase the risk of ventricular arrhythmias.^[1] It is also contraindicated in individuals with a history of significant arrhythmias, as these conditions heighten the susceptibility to torsades de pointes and sudden cardiac death. Hypokalemia or hypomagnesemia should be corrected prior to initiation of therapy.^[1] Use with caution in patients with recent myocardial infarction or other cardiac disorders. Additional precautions include avoiding use in patients with known QT interval prolongation. Pimozide should be used with caution in patients with severe bradycardia or uncompensated heart failure, which can exacerbate the arrhythmogenic effects.^[1] Known hypersensitivity to pimozide or other diphenylbutylpiperidine derivatives represents another absolute contraindication, potentially resulting in severe allergic reactions.^[1] Concomitant use with strong CYP3A4 inhibitors, such as ketoconazole, is contraindicated owing to the risk of elevated pimozide plasma levels and resultant toxicity, including enhanced QT prolongation.^[1] Pimozide is not recommended in children under 12 years of age, as safety and efficacy have not been established in this population.^[1] In elderly patients, while not absolutely contraindicated, extreme caution is advised due to their elevated risk of arrhythmias and other adverse cardiac events. Pimozide is not approved for the treatment of behavioral disorders in elderly patients with dementia due to an increased risk of death.^[27]^[1] Regarding pregnancy, pimozide is classified as FDA Pregnancy Category C, and its use should be avoided unless the potential benefits justify the risks, given the possibility of neonatal extrapyramidal symptoms or withdrawal.^[1] Use during lactation is not recommended; it is unknown if pimozide is excreted in human milk, and a decision should be made whether to discontinue nursing or the drug.^[1]

Drug Interactions

Pimozide, a typical antipsychotic, exhibits significant drug interactions primarily through pharmacodynamic effects on cardiac repolarization and pharmacokinetic alterations via cytochrome P450 enzymes. These interactions can lead to increased risk of torsades de pointes, ventricular arrhythmias, and elevated pimozide exposure, necessitating careful avoidance or monitoring in clinical practice.^[6]

QT-Prolonging Drugs

Pimozide blocks the hERG potassium channel, prolonging the QT interval, and coadministration with other QT-prolonging agents results in additive effects that heighten the risk of serious ventricular arrhythmias. Concomitant use is contraindicated with antiarrhythmic agents such as quinidine, procainamide, amiodarone, and sotalol, as well as Class Ia and III antiarrhythmics like dofetilide.^[6] Similarly, macrolide antibiotics including erythromycin and clarithromycin are contraindicated due to their QT-prolonging properties and inhibition of pimozide metabolism.^[6] Fluoroquinolones such as moxifloxacin, gatifloxacin, and sparfloxacin also pose a contraindication for the same reasons.^[6] Other examples include certain antipsychotics (e.g., thioridazine, ziprasidone), antidepressants (e.g., tricyclics), and antimalarials (e.g., halofantrine, mefloquine). Management involves strict avoidance of these combinations; if unavoidable, baseline and serial ECG monitoring for QTc prolongation is essential, with discontinuation if QTc exceeds 500 ms or increases by more than 60 ms from baseline.^[6]^[28]

CYP3A4 Inhibitors

Pimozide is primarily metabolized by CYP3A4, and strong inhibitors substantially elevate its plasma levels, increasing toxicity risks such as QT prolongation and extrapyramidal symptoms. Strong CYP3A4 inhibitors like azole antifungals (e.g., itraconazole, ketoconazole) can increase pimozide exposure by 3- to 10-fold, rendering coadministration contraindicated.^[6] Macrolides such as erythromycin and clarithromycin similarly inhibit CYP3A4 and are contraindicated for their dual pharmacokinetic and pharmacodynamic effects.^[6] Moderate CYP3A4 inhibitors, including protease inhibitors (e.g., ritonavir, indinavir) and nefazodone, require dose reduction of pimozide and close monitoring of plasma levels and ECG.^[6] Grapefruit juice, a mild CYP3A4 inhibitor, should also be avoided to prevent elevated pimozide concentrations.^[6] According to pharmacogenetic guidelines, interaction checkers and therapeutic drug monitoring are recommended prior to initiating therapy in patients on these agents.^[28]

CYP2D6 Inhibitors

As a substrate of CYP2D6, pimozide's exposure increases with strong inhibitors of this enzyme, particularly in poor or intermediate metabolizers. Paroxetine, a potent CYP2D6 inhibitor, significantly raises pimozide levels and is contraindicated due to enhanced risk of QT prolongation and cardiac events.^[6] Other strong CYP2D6 inhibitors like fluoxetine necessitate pimozide dose adjustments, with monitoring of serum levels and ECG recommended; genotyping for CYP2D6 status is advised for doses exceeding 4 mg/day in adults or 0.05 mg/kg/day in children to guide dosing.^[29]^[30] Sertraline and other specified SSRIs also interact via CYP2D6 inhibition and are contraindicated.^[6]

Other Interactions

Pimozide can potentiate central nervous system depression when combined with alcohol, benzodiazepines, or other sedatives, leading to increased sedation and impaired psychomotor function; caution and dose adjustments are advised.^[6] Concomitant use with levodopa or other dopamine agonists may exacerbate extrapyramidal symptoms due to pimozide's dopamine D2 receptor antagonism.^[31] Antihypertensive agents, particularly those affecting alpha-adrenergic receptors, can enhance pimozide-induced hypotension, requiring blood pressure monitoring.^[31] The 2023 Dutch Pharmacogenetics Working Group guidelines emphasize using interaction checkers and considering CYP1A2 inhibitors (e.g., certain SSRIs) in polypharmacy scenarios to mitigate cumulative risks.^[28]

Pharmacology

Pharmacodynamics

Pimozide exerts its primary antipsychotic and antitic effects through antagonism of dopamine receptors, particularly the D2, D3, and D4 subtypes, with high binding affinity at these sites. It displays a Ki value of approximately 1.4 nM at the D2 receptor, enabling potent blockade of dopaminergic neurotransmission in the mesolimbic pathway, which suppresses excessive dopamine signaling implicated in psychosis and tic disorders.^[32] This selective inhibition in key brain regions reduces hallucinatory and delusional symptoms as well as motor and vocal tics by normalizing hyperdopaminergic activity.^[31] In addition to its dopaminergic actions, pimozide antagonizes the 5-HT7 serotonin receptor with a Ki of about 0.5 nM, potentially contributing to anxiolytic and mood-stabilizing effects observed in clinical use. It also interacts with the sigma-1 receptor, where its binding affinity supports a possible neuroprotective role, though functional details remain under investigation. However, pimozide potently blocks the hERG potassium channel responsible for cardiac repolarization, with an IC50 of approximately 18-20 nM, which underlies its risk of QT interval prolongation and torsades de pointes.^[33]^[34] Therapeutically, pimozide modulates basal ganglia circuits via D2 receptor antagonism to decrease tic frequency in conditions like Tourette's syndrome. Blockade of D2 receptors in the tuberoinfundibular pathway leads to elevated prolactin levels by removing tonic dopaminergic inhibition of lactotroph cells in the pituitary. Notably, pimozide lacks significant affinity for muscarinic acetylcholine or alpha-adrenergic receptors, which limits anticholinergic side effects such as dry mouth and cognitive impairment, as well as orthostatic hypotension.^[35]^[36]^[37] At therapeutic doses of 1-10 mg daily, pimozide achieves 60-80% occupancy of central D2 receptors, a level associated with clinical efficacy against tics and psychosis while increasing the risk of extrapyramidal symptoms due to nigrostriatal pathway involvement.^[38]

Pharmacokinetics

Pimozide is administered orally and exhibits an absolute bioavailability of greater than 50%, with significant first-pass metabolism occurring in the liver.^[1] Peak plasma concentrations are typically achieved 6 to 8 hours after dosing, with a range of 4 to 12 hours, reflecting slow absorption.^[1] Following absorption, pimozide is highly bound to plasma proteins, approximately 99%, which limits its free fraction in circulation.^[39] The apparent volume of distribution is large, estimated at 15 to 20 L/kg, indicating extensive tissue distribution.^[40] It readily crosses the blood-brain barrier, facilitating its central nervous system effects.^[41] Pimozide undergoes extensive hepatic metabolism primarily via the cytochrome P450 enzyme CYP3A4, with minor contributions from CYP1A2 and CYP2D6.^[1] Key metabolites include 5-hydroxypimozide, 6-hydroxypimozide, and 1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one (DHPBI), which are considered inactive.^[42] The elimination half-life of pimozide is approximately 55 hours in patients with schizophrenia, with considerable interindividual variability (up to 13-fold in area under the curve and peak levels).^[1] Less than 1% of the unchanged drug is excreted renally, while the majority of elimination occurs via renal excretion of metabolites, with the kidney serving as the primary route for their clearance.^[43]^[1] Genetic polymorphisms in CYP2D6 significantly influence pimozide pharmacokinetics; poor metabolizers, comprising 5-10% of the population (approximately 7% in Caucasians), exhibit 2- to 3-fold higher plasma exposure, necessitating dose adjustments and closer monitoring.^[1] Steady-state concentrations are generally reached within 1 to 2 weeks, particularly extended in poor metabolizers.^[1]

Toxicology

Overdose Symptoms

Pimozide overdose manifests as an acute exaggeration of its pharmacologic effects, primarily involving severe extrapyramidal symptoms (EPS) such as dystonia and parkinsonism, which can onset within hours of ingestion. These motor disturbances include muscle trembling, jerking, stiffness, and uncontrolled movements, often more intense than those seen at therapeutic doses. Sedation progressing to coma, hypotension, and tachycardia are also common early features, alongside troubled or shallow breathing due to respiratory depression.^[1]^[4] Cardiac toxicity represents the most life-threatening aspect, characterized by QT interval prolongation often exceeding 500 ms, which predisposes to ventricular arrhythmias such as torsades de pointes and potentially sudden death. This risk peaks within the first 24-48 hours post-ingestion, as evidenced by case reports of patients developing torsades after ingesting 800 mg, with QT normalization occurring days later following supportive care. Pimozide has been associated with serious cardiac reactions, including fatalities primarily from dysrhythmias.^[1]^[44]^[45] Additional manifestations in massive overdose include anticholinergic toxicity, leading to delirium, and grand mal seizures, though respiratory depression remains a key concern. These symptoms overlap with but are more severe than routine adverse effects like mild EPS observed during therapeutic use.^[46]^[1] Toxicity typically emerges at single doses exceeding 20 mg, far above the recommended maximum of 10 mg daily, with severe outcomes reported at much higher levels such as 800 mg. While exact lethal doses vary, sudden deaths have been linked to high-dose exposures, particularly in the context of QT prolongation.^[1]^[44] Vulnerable populations include children, in whom even 0.5 mg/kg (e.g., 6 mg in an 18-month-old) can cause significant hypotension, drowsiness, and delayed dystonia; the elderly, who experience heightened EPS risk; and individuals with preexisting cardiac conditions, where baseline QT abnormalities amplify arrhythmogenic potential. In extreme cases, the hyperthermia, rigidity, and autonomic instability may mimic neuroleptic malignant syndrome.^[46]^[1]

Overdose Management

Management of pimozide overdose begins with immediate assessment and stabilization of the patient's airway, breathing, and circulation (ABCs), including establishment of a patent airway and mechanical ventilation if respiratory depression occurs.^[1] Gastrointestinal decontamination is recommended if ingestion was within 2 hours; this includes gastric lavage for large amounts and administration of activated charcoal to adsorb the drug, as pimozide binds well to charcoal.^[47] There is no specific antidote for pimozide overdose.^[48] Cardiac monitoring is essential due to the risk of QT prolongation and torsades de pointes; continuous electrocardiographic (ECG) monitoring should be performed until normalization.^[1] For torsades de pointes, intravenous magnesium sulfate (typically 1-2 g over 1-2 minutes, followed by infusion) is the first-line treatment, even if serum magnesium levels are normal.^[49] Class Ia and Ic antiarrhythmics should be avoided, as they may exacerbate QT prolongation; temporary cardiac pacing may be required for refractory cases.^[47] Hypotension should be managed with intravenous fluids; if unresponsive, vasopressors such as norepinephrine or phenylephrine can be used, but epinephrine should be avoided.^[1] Neurological complications require targeted interventions: benzodiazepines (e.g., lorazepam or diazepam) are indicated for seizures or agitation.^[47] Extrapyramidal symptoms (EPS), such as dystonia or akathisia, should be treated with anticholinergics like benztropine or diphenhydramine.^[48] If neuroleptic malignant syndrome is suspected, immediate discontinuation of pimozide and supportive care are critical, with dantrolene for severe rigidity and hyperthermia.^[48] Electrolyte imbalances, particularly hypokalemia and hypomagnesemia, must be corrected promptly to mitigate cardiac risks.^[47] Supportive measures include intravenous fluids for volume resuscitation and monitoring for complications such as rhabdomyolysis or renal failure. Hemodialysis is ineffective due to pimozide's high protein binding and large volume of distribution.^[47] Patients should be observed for at least 4 days given the drug's long half-life (approximately 55 hours), with extension to 72 hours or longer based on clinical stability.^[1] These protocols align with current toxicology guidelines, such as those in Goldfrank's Toxicologic Emergencies, emphasizing supportive care over elimination enhancement.^[50]

History

Development

Pimozide was synthesized in 1963 at Janssen Pharmaceutica in Belgium as part of the diphenylbutylpiperidine class of antipsychotics, marking it as a novel neuroleptic with high potency relative to chlorpromazine (ratio of 50-70:1).^[51]^[52] The compound was developed under the leadership of Paul Adriaan Jan Janssen, the founder of Janssen Pharmaceutica, who oversaw the creation of numerous psychotropic agents during the 1960s, including this orally long-acting drug aimed at enhancing neuroleptic efficacy.^[53]^[54] Early research in the 1960s focused on pimozide's potential for treating schizophrenia, where preclinical studies demonstrated its strong dopamine D2 receptor antagonism, positioning it as a potent antipsychotic comparable to established agents like chlorpromazine in efficacy.^[55]^[54] Animal models during this period also revealed pimozide's ability to suppress tics through dopaminergic blockade, laying groundwork for its later applications beyond psychosis.^[56] Clinical trials in the late 1960s led to European approvals for psychosis and schizophrenia, with pimozide first marketed as Orap in several countries during that decade.^[57] In the United States, trials shifted toward Tourette's syndrome in the 1980s following its designation as an orphan drug under the 1983 Orphan Drug Act, culminating in FDA approval in 1984 specifically for suppressing motor and phonic tics in patients unresponsive to other therapies.^[58]^[59] Pre-approval challenges emerged from early reports of QT interval prolongation during 1970s and 1980s investigations, prompting label warnings for cardiac monitoring to mitigate risks of ventricular arrhythmias even before full market entry.^[60]

Regulatory Approvals

Pimozide received approval from the US Food and Drug Administration (FDA) on July 31, 1984, as an orphan drug for the suppression of motor and phonic tics in patients with Tourette's disorder, under New Drug Application (NDA) 017473.^[58]^[22] The FDA label includes a boxed warning for QT interval prolongation, which increases the risk of torsade de pointes and sudden death, and this warning has been present since at least the early 2000s based on post-approval cardiac safety data.^[6] In 2011, the FDA approved a supplemental application (S-046) updating the label to incorporate clinical drug interaction studies, emphasizing contraindications with strong CYP2D6 and CYP3A4 inhibitors such as paroxetine, due to increased risk of QT prolongation and arrhythmias.^[1]^[61] In Europe, pimozide has been authorized nationally since the late 1960s for the treatment of schizophrenia and chronic psychoses; it has also been used for motor tics in Tourette's syndrome.^[57]^[62] As of 2025, its authorization under the European Medicines Agency (EMA) framework remains in place for schizophrenia and chronic psychoses in certain member states, with ongoing periodic safety update reports monitoring cardiac risks.^[63] Due to concerns over QT prolongation and sudden cardiac events reported in post-marketing surveillance, use has been restricted or contraindicated in patients with cardiac risk factors across European markets.^[45] Pimozide is available in Canada and Australia for the management of Tourette's syndrome, where it is supplied through licensed pharmacies and remains indicated for tic suppression.^[64]^[65] Post-marketing surveillance from the 1990s through the 2020s has led to additional contraindications for concomitant use with CYP3A4 and CYP2D6 inhibitors, based on reports of elevated plasma levels and enhanced arrhythmogenic potential, with no new indications approved by 2025.^[1]^[11] Generic versions of pimozide became available in the US in the late 1990s, with Teva Pharmaceuticals receiving approval for the 1 mg strength in August 1997 and serving as a primary supplier thereafter.^[66]^[67]

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Antipsychotic Medications - StatPearls - NCBI Bookshelf - NIH
Feb 26, 2023 · Contraindications · History of severe allergy · Use of central nervous system depressants like barbiturates, benzodiazepines, opioids · With ...
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Dutch Pharmacogenetics Working Group (DPWG) guideline for the ...
Mar 31, 2023 · A guideline describing the gene-drug interaction between the genes CYP2D6, CYP3A4 and CYP1A2 and antipsychotics is presented here.
[28]
Table of Pharmacogenetic Associations - FDA
Coadministration with strong CYP3A inhibitors is contraindicated in intermediate and poor CYP2D6 metabolizers.
[29]
Annotation of DPWG Guideline for pimozide and CYP2D6 - ClinPGx
Patients who are CYP2D6 intermediate metabolizers should be given no more than 80% of the standard maximum dose of pimozide while patients who are CYP2D6 ...
[30]
Pimozide: Uses, Interactions, Mechanism of Action | DrugBank Online
Pimozide is an antipsychotic used to manage debilitating motor and phonic tics in patients with Tourette's Disorder.
[31]
https://go.drugbank.com/drugs/DB01100
[32]
Pimozide | Non-selective Dopamine - Tocris Bioscience
$$45 deliveryPimozide is a dopamine D2-receptor antagonist and antipsychotic which binds with very high affinity to the cloned rat 5-HT7 receptor (Ki = 0.5 nM). Compound ...Missing: Ki | Show results with:Ki
[33]
High affinity blockade of the HERG cardiac K(+) channel ... - PubMed
Using patch clamp electrophysiology, we found that pimozide was a potent inhibitor of HERG displaying an IC(50) value of 18 nM. In contrast, pimozide (10 microM) ...
[34]
Merging the Pathophysiology and Pharmacotherapy of Tics - PMC
Jan 9, 2019 · Anatomically, cortical-basal ganglia-thalamo-cortical (CBGTC) circuits have an essential role in the expression of tics.
[35]
Role of dopamine in the inhibitory control of growth hormone and ...
As expected, plasma prolactin levels were elevated following pimozide treatment due to the removal of inhibitory dopaminergic control.
[36]
Antipsychotic Medications - Psychiatric Disorders - Merck Manuals
High-potency antipsychotics (eg, haloperidol) have a higher affinity for dopamine receptors and less of an affinity for alpha-adrenergic and muscarinic ...
[37]
All Roads to Schizophrenia Lead to Dopamine Supersensitivity and ...
Five dopamine receptors have been found: D1, D2, D3, D4, and D5. The D2 ... But when one calculates the ratio of the Ki values for D2 receptors divided ...
[38]
Pimozide: Uses, Dosage, Side Effects and More | MIMS Singapore
Distribution: Plasma protein binding: 99%. Metabolism: Extensively metabolised in the liver via N-dealkylation mainly by CYP3A4 isoenzyme, and to a lesser ...<|separator|>
[39]
Sensitive assay for pimozide in human plasma using high ...
Volume of distribution/F (l), 1071. Total clearance/F (ml/h), 32.7. 4. Discussion. This paper describes a specific and sensitive method to quantitate pimozide ...
[40]
Pimozide - an overview | ScienceDirect Topics
Pimozide is oxidized by two CYP isoforms, CYP3A4 and CYP1A2, with the former being the responsible isoform at therapeutically relevant pimozide concentrations.
[41]
Pimozide Pathway, Pharmacokinetics - ClinPGx
Metabolism. Pimozide is mainly metabolized to three products: 6-hydroxypimozide, 5-hydroxypimozide and 1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one ( ...
[42]
Pimozide: Uses, Side Effects & Dosage | Healio
This medication is used to reduce uncontrolled movements (motor tics) or outbursts of words/sounds (vocal tics) caused by Tourette syndrome. ... Fda Approved:.
[43]
Case report: reversible QT prolongation with torsades de pointes in ...
The authors describe a patient in whom torsades de pointes developed after the ingestion of 800 mg pimozide as a suicide attempt.
[44]
Pimozide - an overview | ScienceDirect Topics
Dystonias are common after pimozide overdose, but occasionally also occur at low doses, as in a 7-year-old boy who developed repeated episodes of acute ...Agent-Agent Interactions · Other Side Effects · A Worldwide Yearly Survey Of...<|control11|><|separator|>
[45]
Delayed dystonia following pimozide overdose in a child - PubMed
In adults, pimozide intoxication may cause seizures, extrapyramidal and anticholinergic effects, hypotension, QTc prolongation and torsades de pointes. We ...
[46]
Neuroleptic Agent Toxicity Treatment & Management
Jul 24, 2025 · Activated charcoal remains the GI decontamination method of choice. Neuroleptics are generally well bound by activated charcoal and should be ...Approach Considerations · Prehospital Care · Emergency Department Care
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Neuroleptic Agent Toxicity - StatPearls - NCBI Bookshelf - NIH
Jul 3, 2023 · The following is a brief review of the most common and life-threatening toxicities associated with the use of neuroleptic agents.
[48]
Torsade de Pointes - StatPearls - NCBI Bookshelf - NIH
The recommended initial dose of magnesium is a slow 2 g IV push. An infusion of 1 gm to 4 gm/hr should be started to keep the magnesium levels greater than 2 ...Continuing Education Activity · Etiology · Epidemiology · Treatment / Management
[49]
Antipsychotics | Goldfrank's Toxicologic Emergencies, 11e
After overdose, antipsychotic toxicity is dose dependent and reflects an extension of the drug's effects on neurotransmitter systems and other biologic ...
[50]
Pimozide and Adipic Acid: A New Multicomponent Crystalline Entity ...
Nov 27, 2024 · Pimozide (PMZ), 1-(1-(4,4-bis(p-fluorophenyl)butyl)-4-piperidyl)-2-benzimidazoline, is a first generation antipsychotic, synthesized in 1963 by ...
[51]
Diphenylbutylpiperidine - an overview | ScienceDirect Topics
Pimozide also inhibits hERG (human Ether-a-go-go-related) K+-Channel (Kongsamut et al., 2002). As in the case for other typical antipsychotics, pimozide binds ...
[52]
Forty years of antipsychotic Drug research--from haloperidol to ...
Aug 8, 2025 · Pimozide (depicted in Fig. 1) is a neuroleptic of the diphenylbutylpiperidine class which was discovered in 1963 by the physician Paul Janssen ( ...
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Pimozide, a Chemically Novel, Highly Potent and Orally ... - PubMed
Pimozide, a Chemically Novel, Highly Potent and Orally Long-Acting Neuroleptic Drug ... 1968 Mar;18(3):279-82. Authors. P A Janssen, F T Allewijn. PMID ...Missing: synthesis 1963
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Pimozide for schizophrenia or related psychoses - PubMed
Pimozide is a drug with similar efficacy to other more commonly used antipsychotics such as chlorpromazine for those with schizophrenia.Missing: EMA | Show results with:EMA
[55]
Animal models of tic disorders: A translational perspective - PMC
Accordingly, dopamine receptor antagonists, such as haloperidol and pimozide, are highly effective in reducing tic severity (Bloch et al., 2011; Roessner et al.
[56]
Pimozide - an overview | ScienceDirect Topics
Rapid administration of pimozide has also led to ECG changes cardiac arrhythmia risk, hypertension, sudden cardiac death, prolongation of the QT interval, and ...Drug Repurposing For Cancer · 4 Pimozide · 4.2 Antiproliferative...
[57]
F.D.A. APPROVES DRUG TO TREAT TOURETTE SYNDROME
Aug 8, 1984 · Pimozide, which has been used to treat schizophrenia, has such side effects as sedation, drowsiness and possible cardiac disruption, and ...
[58]
Pimozide: Use in Tourette's Syndrome - Donald C. McLeod, Carol L ...
Clinical trials with pimozide demonstrate a positive response for many patients, although superiority over haloperidol has not been demonstrated in general.
[59]
Changes in the Product Label for Pimozide Illustrate Both the ...
Sep 15, 2012 · ... pimozide-induced QT prolongation by the FDA and the manufacturer. On ... pimozide was being developed in the 1970s and early 1980s.
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[PDF] Orap (pimozide) 1 mg and 2 mg Tablets - accessdata.fda.gov
Sep 27, 2011 · It is approved, effective on the date of this letter, for use as recommended in the enclosed, agreed-upon labeling text. CONTENT OF LABELING. As ...
[61]
Pimozide: An Old Wine in a New Bottle! - PMC - NIH
Pimozide, an orphan drug, is FDA-approved for treating Tourette syndrome. Sallee et al. [5] have found it superior to haloperidol with less neurologic side ...
[62]
PSUSA/00002413/202502 - periodic safety update report single ...
Oct 6, 2025 · Periodic safety update report single assessments (PSUSAs) are single assessments of related periodic safety update reports (PSURs) for ...Missing: approval | Show results with:approval
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Pimozide Prices - U.S. & International | PharmacyChecker.com
4.6 430 Price includes $14.95 Shipping. Ships Worldwide except Canada from Australia, Canada, India, Mauritius, New Zealand, United States. CanadaPharmacyPro.com.
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Buy Orap 2 mg Generic from Canada - Canadian Pharmacy World
Free deliveryCanadianpharmacyworld.com offers the generic Orap Pimozide 2 mg from Canada. It is available in the quantity of 100 tablets. For more information and ...
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Generic Orap Availability - Drugs.com
Oct 8, 2025 · Orap is a brand name of pimozide, approved by the FDA in the following formulation: ORAP (pimozide - tablet; oral). Manufacturer, Approval date ...Missing: 017473 | Show results with:017473
[66]
[PDF] Orap (pimozide) tablets - accessdata.fda.gov
Dec 1, 2010 · This supplemental new drug application provides for revisions to the labeling for Orap ... revised to be consistent with the labeling changes ...