Majeptil (thioproperazine)

Majeptil (thioproperazine)

Brand name: Majeptil®.
Active ingredient name: Thioproperazine.
Type of medication: Typical antipsychotic.
Available in Canada from: Erfa Canada Inc. (brand name only).
Form: Oral tablets.
Generic: No.
Listed on Ontario formulary: No.
OHIP+ coverage: No.
Note: Although this medication is available in Ontario, it is not routinely used and is not covered by the provincial drug plans. It may be used in other countries. 

What is Majeptil used for?

Majeptil is used to treat schizophrenia and other psychotic illnesses in adults and children over 10 years old, including people who did not respond to the usual antipsychotics. It may also be used to treat manic episodes in bipolar disorder.

How should I take Majeptil?

  • Majeptil is available in 10 mg tablets.
  • Adults: The starting dose is usually 5 mg a day in a single dose or divided doses. The usual optimal dose is 30 mg - 40 mg per day, but your doctor may adjust your dose up or down according to your response.
  • Children (over 10 years old): The starting dose is usually 1 mg - 3 mg a day in a single dose or divided doses. Your child’s doctor will decide what the best dosage is for your child.

What are the most common side effects seen with Majeptil? 

Because studies have shown an increased risk of death in elderly people with dementia, Majeptil should not be used for this group.
The most common side effects of Majeptil include:
  • Abnormal movements (extrapyramidal symptoms)
  • Changes in monthly menstrual cycle (amenorrhea)
  • Decreased sexual interest and/or function
  • Swelling of breasts and milk production in males and females
  • Difficulty sleeping
  • Constipation
  • Reduced amount of urine
  • Dizziness
  • Drowsiness
  • Dry mouth
  • Nausea
  • Headache
  • Weight changes
  • Blurred vision

What are rare but potentially serious adverse effects with Majeptil?

  • Decrease in white blood cell count (agranulocytosis)
  • Neuroleptic malignant syndrome (NMS)
  • Sudden cardiac death (heart attack)
  • Torsades de pointes (serious heart arrhythmia)


Elderly individuals with dementia-related psychosis treated with antipsychotic medication are at an increased risk of death compared to individuals not receiving antipsychotics. Most deaths appear to be either cardiovascular or infectious. Majeptil is not approved for the treatment of dementia-related psychosis. Some individuals with dementia may, however, be treated with this medication. Discuss the potential risks and benefits of this medication with your doctor for this indication.

What medications interact with Majeptil?

Tell all your doctors, pharmacists and dentist that you are taking Majeptil. You should also tell your doctor or pharmacist if you are taking any other medications, including those obtained without a prescription, and herbal and vitamin products.

The following types of medications might interact with Majeptil:

  • Certain medications for allergies (e.g., Benadryl [diphenhydramine])
  • Certain medications for sleep (e.g., lorazepam, zopiclone)
  • Certain medications for pain (e.g., fentanyl)
  • Anti-Parkinson agents
Avoid drinking alcohol or using illegal drugs while taking Majeptil.