Pimozide (Orap)

What it treats

Pimozide is FDA-approved for the suppression of motor and phonic tics in Tourette syndrome in people who haven't responded to first-line treatments. Other options like clonidine, guanfacine, and some atypical antipsychotics are usually tried first. Pimozide has a role when tics remain disabling and other options have fallen short.

How it works

Pimozide is a selective dopamine D2 receptor antagonist. Blocking D2 quiets dopamine signaling in circuits linked to tics. It has less activity at histamine, muscarinic, and alpha-adrenergic receptors than the sedating phenothiazines, but its effect on the heart's electrical rhythm is more prominent than most antipsychotics, which is why the safety framework is stricter.

Receptor mechanism (detail)

Pimozide is a selective D2 antagonist with additional activity at calcium channels that likely contributes to its QTc-prolonging effect. It's metabolized primarily by CYP3A4 and CYP2D6, so drugs and foods that affect these enzymes can meaningfully raise pimozide levels and QTc risk.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

For Tourette syndrome, a common starting dose is 1 to 2 mg per day. Doses are titrated slowly to effect, often up to a range of 7 to 10 mg per day in adults. In children, dosing is weight-based and usually lower. Anyone identified as a CYP2D6 poor metabolizer is capped at a maximum of 4 mg per day. The prescriber sets and adjusts the dose based on response, side effects, and ECG findings.

Safety monitoring

• ECG at baseline and periodically during dose changes to check the QTc interval. This isn't optional with pimozide.
• CYP2D6 genotyping is recommended before doses exceed 4 mg per day in adults or 0.05 mg/kg per day in children.
• Potassium and magnesium at baseline, low levels raise QTc risk.
• Involuntary-movement screen (AIMS) every six months.
• Movement side-effect check at each early visit.
• Metabolic labs, weight, BMI, fasting glucose or HbA1c, and lipids at baseline and annually.
• Prolactin if symptoms appear.

Metformin co-commencement: Aoife Carolan / Schizophrenia Bulletin guideline.

A clinical guideline led by Aoife Carolan strongly recommends co-commencing metformin alongside high-risk antipsychotics like olanzapine or clozapine. This proactive approach helps mitigate severe metabolic side effects, significantly reducing antipsychotic-induced weight gain and improving insulin resistance. The Schizophrenia Bulletin guideline states that when prescribing olanzapine or clozapine, metformin should be initiated immediately to prevent weight gain and cardiometabolic issues. Pimozide is a first-generation antipsychotic and isn't on the automatic co-commencement list, but metformin is recommended if weight rises more than 3 percent of pre-medication weight or if other cardiometabolic risk factors are present.

Typical titration used in the guideline: 500 mg once daily, then 500 mg twice daily after one week, then 500 mg increments every two weeks as tolerated, up to 1000 mg twice daily by about week six. Contraindicated with eGFR below 30 mL/min/1.73 m². Renal function is checked annually and metformin is held during acute illness or dehydration.

Source: Carolan A, et al. Metformin for the Prevention of Antipsychotic-Induced Weight Gain: Guideline Development and Consensus Validation. Schizophrenia Bulletin. 2025;51(5):1193 to 1203.

What to expect

Common side effects

• Sedation, usually mild.
• Parkinsonism, tremor, stiffness.
• Akathisia.
• Dry mouth, constipation.
• Raised prolactin.
• Weight gain.

Serious side effects and warnings

Boxed warning. Pimozide carries the FDA boxed warning that antipsychotics increase the risk of death in older adults with dementia-related psychosis, and it isn't approved for that use. The label also emphasizes QTc prolongation risk and drug interaction risk more prominently than most antipsychotic labels.

• QTc prolongation and arrhythmia risk. This is the standout serious risk. Baseline and follow-up ECGs matter. Certain drug combinations are contraindicated.
• Drug interactions. CYP3A4 inhibitors (clarithromycin, erythromycin, ketoconazole, some antivirals) and CYP2D6 inhibitors (fluoxetine, paroxetine, bupropion) can raise pimozide levels. Combining pimozide with other QTc-prolonging drugs adds risk.
• Tardive dyskinesia. Long-term antipsychotic use can produce involuntary movements.
• Neuroleptic malignant syndrome. Rare but serious.
• Seizure threshold lowering.

This isn't medical advice. Any concern about a serious side effect should be raised with a prescriber promptly.

Sexual side effects

Pimozide can affect sex drive and function through prolactin elevation. If sexual side effects appear, it's worth raising with the prescriber.

Weight, appetite, and sleep

Weight gain is possible but generally modest at the low doses used for Tourette syndrome. Sleep is usually minimally affected.

Starting and dosing basics

This section is general background, not a dosing instruction. Pimozide comes as tablets. It can be taken with or without food, but grapefruit juice should be avoided because it inhibits CYP3A4 and raises pimozide levels.

Missed doses and interactions

If you miss a dose, take it when you remember unless it's almost time for the next one, then skip and carry on. Don't double up.

Drug interactions are unusually important with pimozide. Several antibiotics, antifungals, antivirals, some antidepressants, and QTc-prolonging drugs are contraindicated or require caution. The prescriber and pharmacist need a full list of medications and supplements before any dose change. Grapefruit juice should be avoided.

Stopping and tapering

Don't stop pimozide abruptly. A prescriber can step the dose down gradually.

Pregnancy and breastfeeding

Untreated severe Tourette syndrome and pimozide use both carry considerations in pregnancy, and pimozide passes into breast milk. Anyone who's pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber. This isn't medical advice.

Cost and generic availability

Pimozide is generic and generally covered by insurance. Cash prices are moderate.

Common questions

Why is CYP2D6 testing recommended? About 7 percent of people of European ancestry are CYP2D6 poor metabolizers. In those individuals, pimozide levels can rise substantially, which raises QTc risk. Testing before going above 4 mg per day helps identify who needs a lower cap.

Why so many drug interactions? Pimozide is metabolized by CYP3A4 and CYP2D6, so anything that inhibits either enzyme can raise pimozide levels. Because pimozide already prolongs QTc, higher levels tip that risk further. Combining it with other QTc-prolonging drugs multiplies the concern.

Is pimozide only used for Tourette syndrome? That's its FDA indication. Off-label use for delusional disorder was once common but has largely been replaced by newer antipsychotics.

Why an ECG? Because QTc prolongation is a real concern with pimozide. A baseline ECG confirms it's safe to start, and follow-up ECGs catch changes as the dose rises.

Questions to ask your prescriber

• What are we hoping this treats, and how will we know it's working?
• Should I be tested for CYP2D6 metabolizer status?
• What medications should I avoid while I'm on pimozide?
• How often should we check an ECG?
• If we decide to stop it later, how would we taper safely?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Pimozide prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Pimozide.
• National Institute of Mental Health. Mental health medications.
• American Academy of Neurology practice parameter on the treatment of Tourette syndrome.
• National Institute for Health and Care Excellence (NICE). CG178, Psychosis and schizophrenia in adults.
• Carolan A, et al. Metformin for the Prevention of Antipsychotic-Induced Weight Gain: Guideline Development and Consensus Validation. Schizophrenia Bulletin. 2025;51(5):1193 to 1203.