Isturisa: Uses, Side Effects and Dosage

What ISTURISA is used for:

ISTURISA is used to treat Cushing’s disease in adults who:

• have had pituitary surgery or radiation treatment, which have not worked to control cortisol levels; or
• cannot have pituitary surgery

How ISTURISA works:

Cushing’s disease is a condition in which the body produces too much of a hormone called cortisol. Too much cortisol may lead to a variety of symptoms such as weight gain (particularly around the waist), a moon-shaped face, bruising easily, irregular periods, excessive body and facial hair, and generally feeling weak, tired or unwell.

ISTURISA blocks the main enzyme that makes cortisol in the adrenal glands. The effect of this is to decrease the over-production of cortisol caused by Cushing’s disease.

The ingredients in ISTURISA are:

Medicinal ingredients: osilodrostat (as osilodrostat phosphate)

Non-medicinal ingredients:

colloidal silicon dioxide, croscarmellose sodium, hypromellose, macrogol, magnesium stearate, mannitol, microcrystalline cellulose, talc, and titanium dioxide (E171), and iron oxides (E172, see below)

• ISTURISA 1 mg tablets contain iron oxide red and iron oxide yellow.
• ISTURISA 5 mg tablets contain iron oxide yellow.
• ISTURISA 10 mg tablets contain iron oxide black, iron oxide red and iron oxide yellow.

ISTURISA comes in the following dosage forms:

Tablets: 1 mg, 5 mg and 10 mg

ISTURISA is available in cartons containing 60 tablets (6 blisters of 10 tablets).

Do not use ISTURISA if:

• You are allergic to osilodrostat, any of the other ingredients of this medicine, or part of the container.

To help avoid side effects and ensure proper use, talk to your healthcare professional before you take ISTURISA. Talk about any health conditions or problems you may have, including if you:

• have or have had heart problems, such as irregular heartbeat, a condition called prolonged QT syndrome, or congestive heart failure.
• have liver problems.
• have kidney problems.
• have or have had low levels of potassium, calcium or magnesium in your blood.
• are of Asian ancestry.

Other warnings you should know about:

• Increased levels of other adrenal hormones

  Treatment with ISTURISA may cause increased levels of other adrenal hormones. This may cause symptoms such as:

  • high blood pressure
  • low potassium levels in your blood
  • swelling
  • acne
  • excessive hair growth (in women)

Contact your healthcare professional if you have any of these side effects.

• Female patients

  Pregnancy and birth control

  • You should not use ISTURISA if you are pregnant, unless your healthcare professional has advised you to do so.
  • If you are able to become pregnant or plan to become pregnant, there are specific risks you should discuss with your healthcare professional.
  • Do NOT become pregnant during treatment with ISTURISA. It may cause harm to your unborn baby.
  • Use effective birth control during treatment with ISTURISA, and for at least 1 week after stopping treatment.
  • Talk to your healthcare professional right away if you become pregnant or think you may be pregnant.

Breastfeeding

• Do NOT breastfeed during treatment with ISTURISA. It is not known if osilodrostat passes through breast milk.
• Talk to your healthcare professional about the best way to feed your baby during treatment with ISTURISA.

• Children and adolescents (under 18 years of age)

  You should not take ISTURISA if you are under 18 years of age. This is because there is a lack of data in these patients.

• Check-ups and testing

  You will have regular visits with your healthcare professional before and during treatment with ISTURISA. They will:

  • Do blood/urine tests. This is to monitor your:

    • Cortisol levels
    • Blood cell count
    • Potassium, calcium and magnesium levels
  • Check the electrical signal of your heart by doing an electrocardiogram (ECG).
  • Do imaging scans to check for signs of pituitary tumour growth.

• Driving and using machinery

  ISTURISA may cause you to have low blood pressure and feel dizzy or tired. Do not drive or use machines if you get these symptoms.

Tell your healthcare professional about all the medicines you take, including any drugs, vitamins, minerals, natural supplements or alternative medicines.

The following may interact with ISTURISA:

• Medicines that may have an unwanted effect (called QT prolongation) on the function of the heart.

• Medicines that can affect electrolyte levels, such as:

  • thiazide and related diuretics (medicines used to treat high blood pressure and fluid retention)
  • laxatives and enemas (medicines used to promote bowel movements and relieve constipation)
  • amphotericin B (medicines used to treat fungal infections)
  • high-dose corticosteroids (medicines that reduce inflammation)
  • proton pump inhibitors (medicines used to decrease the amount of acid produced by the stomach)

These medicines may increase the risk of QT prolongation.

• Enzyme inhibitors or inducers: Medicines that strongly inhibit or induce multiple enzymes, such as:

  • ketoconazole, itraconazole (medicines used to treat fungal infections)
  • clarithromycin, rifampin (medicines used to treat bacterial infections)
  • carbamazepine, phenobarbital (medicines used to treat seizures)
• Theophylline (medicine used to treat breathing problems)
• Tizanidine (medicine used to treat muscle pain and muscle cramps)
• S-mephenytoin (medicine used to treat seizures and bipolar disorder)
• Caffeine
• Omeprazole (medicine used to treat excess stomach acid)
• Dextromethorphan (medicine used to treat cough and flu)
• Midazolam (medicine used for sedation and to help sleep)

How to take ISTURISA:

• Always take ISTURISA exactly as your healthcare professional has told you. Check with your healthcare professional if you are not sure.

• Take by mouth with or without food.

Usual dose:

Adults: 2 mg (two 1 mg tablets) orally twice a day, about every 12 hours.

• You may need a lower starting dose if you are of Asian ancestry or have liver problems.

• After starting treatment, your healthcare professional may need to change your dose, temporarily stop or completely stop your treatment with ISTURISA. This will depend on:

  • how you respond to treatment
  • if you experience side effects, or your cortisol level gets too low
• Do NOT stop taking ISTURISA unless your healthcare professional tells you to. If you stop your treatment with ISTURISA, your cortisol level may become too high.
• Maximum daily dose is 30 mg twice a day.

Overdose:

Overdose with ISTURISA can cause severely low cortisol levels. Signs of severely low cortisol levels include: nausea, vomiting, fatigue, low blood pressure, abdominal pain, loss of appetite, dizziness and fainting.

If you think you have taken too much ISTURISA, your healthcare professional will measure your cortisol levels. If necessary, you may also need to have additional treatment with corticosteroids. Your healthcare professional will continue to monitor you until your condition stabilizes.

Missed dose:

• If you forget to take your dose of ISTURISA, wait until it is time for your next dose and take it at the scheduled time.
• Do NOT take a double dose to make up for a forgotten dose.

Possible side effects from using ISTURISA:

These are not all the possible side effects you may have when taking ISTURISA. If you experience any side effects not listed here, tell your healthcare professional.

• tiredness (fatigue)
• vomiting
• nausea
• decreased appetite
• diarrhea
• abdominal pain
• build-up of fluid leading to swelling, particularly of your ankles
• abnormal blood tests (increased levels of testosterone, low levels of potassium, low blood sugar, decrease in hemoglobin, high cholesterol)
• abnormal results of liver function tests
• dizziness
• headache
• skin rash
• back pain
• muscle and joint pain
• fast heartbeat
• general feeling of being unwell (malaise)
• excessive facial or body hair growth (hirsutism)
• hair loss
• acne
• excessive sweating
• anxiety
• depression

Serious side effects and what to do about them

If you have a troublesome symptom or side effect that is not listed here or becomes bad enough to interfere with your daily activities, tell your healthcare professional.

Reporting side effects

Storage:

• Store at 20°C to 25°C. Protect from moisture.
• Keep out of reach and sight of children.
• Do not use ISTURISA after the expiry date which is stated on the carton and on the blister as EXP. The expiry date refers to the last day of that month.
• Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.

If you want more information about ISTURISA:

• Talk to your healthcare professional.
• Find the full product monograph that is prepared for healthcare professionals and includes this Patient Medication Information by visiting the Health Canada Drug Products Databse website: (https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-product-database.html; the manufacturer’s website https://www.recordatirarediseases.com/ca, or by calling 1-877-827-1306.

Date of Authorization: 2025-07-03