How does this medication work? What will it do for me?

Pimozide belongs to the class of medications called antipsychotics. It is used to manage symptoms of certain types of chronic schizophrenia. It works by affecting the way messages are sent in the central nervous system.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

pms-pimozide is no longer being manufactured for sale in Canada. For brands that may still be available, search under pimozide. This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.

How should I use this medication?

Adults: The recommended starting dose of pimozide ranges from 2 mg to 4 mg once daily, taken in the morning. Your doctor will gradually increase your dose to a maximum of 20 mg daily. The goal is to find the dose where the best effects occur with the least side effects.

Seniors: The recommended starting dose of pimozide ranges from 1 mg to 2 mg once daily, taken in the morning. Your doctor will gradually increase your dose to a maximum of 20 mg daily. The goal is to find the dose where the best effects occur with the least side effects.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take pimozide if you:

  • are allergic to pimozide or to any of the ingredients of the medication
  • are sedated or unconscious
  • have brain damage
  • are taking any of the classes of medications known as "azole" antifungals, antiviral protease inhibitors, or macrolide antibiotics (erythromycins)
  • are taking sertraline, citalopram, escitalopram, or paroxetine
  • are treating tics other than those caused by Tourette’s Disorder
  • have depression
  • have or have a family history of certain types of abnormal heart rhythms
  • have a severely reduced heart rate
  • have a blood disorder
  • have a liver disorder
  • have low blood potassium or magnesium levels
  • have Parkinson's disease
  • have reduced kidney function
  • are scheduled for regional or spinal anaesthetic

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • constipation
  • decreased interest in sexual activity
  • decreased sweating
  • difficulty holding urine
  • dizziness
  • drowsiness
  • dry mouth
  • fatigue
  • lightheadedness, or fainting when rising from a lying or sitting position
  • menstrual changes
  • sinus congestion
  • weight changes

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • blurred vision or other vision problems
  • confusion
  • excessive sweating
  • fast or irregular heartbeat
  • inability to move eyes
  • increased blinking or eyelid spasms
  • lack of facial expression
  • lip smacking or puckering
  • loss of balance control
  • mood or behaviour changes
  • movement disorders (e.g., continuous muscle spasms and contractions, slow movements, irregular, jerky movements, tremor, inability to move eyes, increased blinking, puffing of cheeks, shuffling walk, tremor)
  • restlessness or need to keep moving
  • signs of a blood clot in the arm or leg (tenderness, pain, swelling, warmth, or redness in the arm or leg) or lungs (difficulty breathing, sharp chest pain that is worst when breathing in, coughing, coughing up blood, sweating, or passing out)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • swelling or soreness of breasts (less common in men)
  • symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
  • symptoms of a lung infection (LRTI) (e.g., shortness of breath, cough, chest pain)
  • uncontrolled chewing movements or uncontrolled movements of the neck, trunk, arms, or legs, including twisting movements
  • unusual secretion of milk (rare in men)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • convulsions (seizures)
  • long-lasting (greater than 4 hours) and painful erection of the penis
  • loss of consciousness (fainting)
  • high or low (irregular) blood pressure
  • signs of neuroleptic malignant syndrome (e.g., confusion, reduced consciousness, high fever, or muscle stiffness)
  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abnormal heart rhythms: This medication can cause abnormal heart rhythms. Certain medications can increase the risk of a type of abnormal heart rhythm called QT prolongation, and should not be used in combination with pimozide. You are more at risk for this type of abnormal heart rhythm and its complications if you:

  • are female
  • are older than 65 years of age
  • have a family history of sudden cardiac death
  • have a history of heart disease or abnormal heart rhythms
  • have a slow heart rate
  • have congenital prolongation of the QT interval
  • have diabetes
  • have had a stroke
  • have low potassium, magnesium, or calcium levels
  • have nutritional deficiencies

If you have heart disease and abnormal heart rhythms, or are taking certain medications (e.g., ketoconazole, atazanavir), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Blood counts: This medication can decrease the number of neutrophils (a type of white blood cell that helps fight infection), red blood cells (which carry oxygen), and platelets (which help your blood to clot). Your doctor will do blood tests to monitor this. If you notice any signs of infection (e.g., fever, chills, or sore throat) or unusual bleeding or bruising, contact your doctor immediately.

Blood pressure: People who take pimozide may develop very low blood pressure causing dizziness and lightheadedness. Some individuals, especially seniors or those who are debilitated, have had temporary low blood pressure for several hours after taking the medication.

Body temperature: Pimozide, like other antipsychotic medications, may interfere with your body's ability to regulate body temperature. People who exercise vigorously, who are exposed to extreme heat, are dehydrated, or are taking anticholinergic medications (e.g., benztropine, oxybutynin) are more at risk. Contact your doctor as soon as possible if you feel very hot and are unable to cool down.

Take care to avoid overheating during strenuous exercise or in hot temperatures, and avoid becoming dehydrated by drinking enough fluids.

Diabetes: Pimozide may cause an increase in blood sugar levels (may cause a loss of blood glucose control) and glucose tolerance may change. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication.

If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Drowsiness/reduced alertness: Pimozide may reduce alertness, especially at the start of treatment. Alcohol may increase this effect. Avoid tasks requiring alertness, such as driving or operating machinery, until you determine if the medication affects you this way.

Grapefruit juice: Grapefruit juice prevents pimozide from being broken down (metabolized) in the body and may cause an increase in side effects. Avoid drinking grapefruit juice if you take pimozide.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Neuroleptic malignant syndrome (NMS): Pimozide, like other antipsychotic medications, can cause a potentially fatal syndrome known as neuroleptic malignant syndrome (NMS). If you notice the symptoms of NMS such as high fever, muscle stiffness, confusion or loss of consciousness, sweating, racing or irregular heartbeat, or fainting, get immediate medical attention.

Seizures: Pimozide may increase the risk of seizures. If you have a history of epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Stopping the medication: Do not stop taking this medication without speaking to your doctor. Stopping suddenly may lead to uncomfortable side effects, such as nausea, vomiting, difficulty sleeping, or unwanted movement. Your doctor may wish to gradually reduce your dose over time.

Tardive dyskinesia (TD): As with all antipsychotic medications, a syndrome called TD may occur for some people on long-term therapy or after they stop taking the medication. The syndrome's main features are rhythmical involuntary movements of the tongue, face, mouth, or jaw. Tell the doctor if you notice these symptoms in yourself or someone else taking pimozide.

Pregnancy: The safe of use of pimozide during pregnancy has not been established. It should not be taken by women who are or may become pregnant, particularly during the first trimester of pregnancy, unless the benefits outweigh the risks.

Breast-feeding: This medication may pass into breast milk. If you are a breast-feeding mother and are taking pimozide, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children. Pimozide is not recommended for children.

Seniors: When used to treat seniors with dementia, other antipsychotic medications have shown an increase in the risk of death as a result of heart attack, stroke, or infection. Pimozide should not be used to treat seniors with dementia.

What other drugs could interact with this medication?

There may be an interaction between pimozide and any of the following:

  • abiraterone
  • aclidinium
  • alcohol
  • alfuzosin
  • amantadine
  • amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
  • antiarrythmics (e.g., amiodarone, disopyramide, dronedarone, flecainide, procainamide, quinidine)
  • antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
  • anti-Parkinsons medications (e.g., amantadine, apomorphine, bromocriptine, levodopa, pramipexole, ropinirole, rotigotine)
  • antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
  • aprepitant
  • atorvastatin
  • atropine
  • azelastine
  • "azole" antifungals (e.g., fluconazole, itraconazole, ketoconazole, voriconazole)
  • barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
  • belladonna
  • benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
  • benztropine
  • bicalutamide
  • bosentan
  • bromocriptine
  • bupropion
  • buspirone
  • calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
  • cannabis
  • celecoxib
  • chloral hydrate
  • chloroquine
  • cinacalcet
  • conivaptan
  • cyclosporine
  • cyproterone
  • danazol
  • deferasirox
  • dexamethasone
  • dextromethorphan
  • domperidone
  • donepezil
  • enzalutamide
  • ergot alkaloids (e.g., ergotamine, dihydroergotamine)
  • ethinyl estradiol
  • famotidine
  • fingolimod
  • flavoxate
  • formoterol
  • galantamine
  • gemfibrozil
  • general anesthetics (medications used to put people to sleep before surgery)
  • glycopyrrolate
  • grapefruit juice
  • HIV protease inhibitors (e.g., atazanavir, darunavir, lopinavir, ritonavir, saquinavir)
  • HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
  • hydroxychloroquine
  • indacaterol
  • ipratropium
  • isoniazid
  • ketotifen
  • lithium
  • lomitapide
  • loperamide
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • magnesium sulfate
  • maprotiline
  • mefloquine
  • methadone
  • metoclopramide
  • metronidazole
  • mifepristone
  • mirabegron
  • mirtazapine
  • mitotane
  • modafinil
  • monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, rasagiline, selegiline, tranylcypromine)
  • muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
  • nabilone
  • narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone)
  • nefazodone
  • nitroglycerin
  • octreotide
  • olodaterol
  • olopatadine
  • oxybutynin
  • pentamidine
  • potassium chloride
  • primaquine
  • quinine
  • quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
  • rifabutin
  • rifampin
  • romidepsin
  • St. John's wort
  • scopolamine
  • seizure medications (e.g., carbamazepine, clobazam, levetiracetam, phenobarbital, phenytoin, primidone, topiramate, valproic acid, zonisamide)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram,  fluoxetine, paroxetine, sertraline)
  • serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
  • serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., desvenlafaxine, duloxetine, venlafaxine)
  • simeprevir
  • sotalol
  • solifenacin
  • sulfamethoxazole
  • tacrolimus
  • tamoxifen
  • terbinafine
  • teriflunomide
  • tetrabenazine
  • tetracyclines (e.g., minocycline, tetracycline)
  • thalidomide
  • ticagrelor
  • ticlopidine
  • tiotropium
  • tocilizumab
  • tolterodine
  • tramadol
  • trazodone
  • trimethoprim
  • tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine)
  •  "triptan" migraine medications (e.g., eletriptan, rizatriptan, sumatriptan)
  • tryptophan
  • tyrosine kinase inhibitors (e.g., dasatinib, imatinib, nilotinib, sunitinib)
  • umeclidinium
  • vardenafil
  • vilanterol
  • zolpidem
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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