Drug Formulary information is intended for use by healthcare professionals. It is not intended to be medical advice. Some of the information, including information about funding for cancer drugs, does not apply to all patients. Cancer treatment plans are unique to each patient. If you are a patient, please speak with your healthcare team to understand how this information applies to you.

drug-infosheet

idelalisib

Cancer Type
Hematologic, Leukemia - Chronic Lymphocytic (CLL), Lymphoma - Non-Hodgkin's Low Grade
Other Names

Zydelig®
Appearance

Tablets in various strengths

idelalisib

Pronunciation:

eye-DEL-a-LIS-ib

Other Name(s):

Zydelig®

Appearance:

Tablets in various strengths

This handout gives general information about this cancer medication.

You will learn:

  • who to contact for help

  • what the medication is

  • how it is given

  • what to expect while on medication

People Talking

This handout was created by Ontario Health (Cancer Care Ontario) together with patients and their caregivers who have also gone through cancer treatment. It is meant to help support you through your cancer treatment and answer some of your questions.

This information does not replace the advice of your health care team. Always talk to your health care team about your treatment.

 

Who do I contact if I have questions or need help?

 

My cancer health care provider is: _____________________________________________

During the day I should contact: _______________________________________________

Evenings, weekends and holidays: _____________________________________________

 

This page gives general information about this cancer medication.

You will learn:

  • who to contact for help

  • what the medication is

  • how it is given

  • what to expect while on this medication

People Talking

This information was created by Ontario Health (Cancer Care Ontario) together with patients and their caregivers who have also gone through cancer treatment. It is meant to help support you through your cancer treatment and answer some of your questions.

This information does not replace the advice of your health care team. Always talk to your health care team about your treatment.

What is this treatment for?

For treating certain blood cancers such as chronic lymphocytic leukemia (CLL) or follicular lymphoma

What should I do before I start this treatment?

Tell your health care team if you have or had significant medical condition(s), especially if you have / had:

  • inflammatory bowel disease,

  • liver problems or hepatitis,

  • severe diarrhea,

  • lung problems,

  • any infections, or 

  • any allergies.
     

Important Icon

Remember To:

 

  • Tell your health care team about all of the other medications you are taking.

  • Keep taking other medications that have been prescribed for you, unless you have been told not to by your health care team.

You will have a blood test to check for hepatitis B before starting treatment. See the Hepatitis B and Cancer Medications pamphlet for more information.

How is this treatment given?
  • This medication is usually taken twice a day by mouth
     
  • Swallow whole with a glass of water, with or without food
     
  • If you miss a dose, take it if it is within 6 hours of the missed dose, otherwise skip and take your next dose as scheduled. Do not double the dose to make up for the forgotten one.

 

Warning: If you take too much of this medication by accident, or if you think a child or a pet may have swallowed your medication, you must call the Ontario Poison Control Center right away at: 1-800-268-9017.

 

Other medications you may be given with this treatment

To Prevent Infection from Bacteria

You may be given a medication to take before your treatment to prevent infection.

  • These are called antibiotics (such as trimethoprim-sulfamethoxazole).


To Treat Diarrhea

This medication can cause diarrhea. Diarrhea is when you have loose bowel movements (watery poo) or you need to go poo (have bowel movements) more often than usual. Diarrhea may start a few days after your treatment begins.

You will be given a medication called loperamide (Imodium®) to help treat your diarrhea. Take to your health care team about how to take it.

Keep your loperamide with you all the time. When diarrhea starts, take the loperamide right away.

DO this while on treatment DO NOT do this while on treatment

Check Mark Icon

  • DO check with your health care team before getting any vaccinations, surgery, dental work or other medical procedures.  

  • DO protect your skin from the sun. Wear a long sleeved shirt, long pants and a hat. Apply sunscreen with UVA and UVB protection and an SPF of at least 30. Your skin may be more sensitive to the sun and you could develop a bad sunburn or rash more easily.

Stop Icon

  • DO NOT take any other medications, such as vitamins, over-the-counter (non-prescription) drugs or substances, or natural health products without checking with your health care team.

  • DO NOT start any complementary or alternative therapies, such as acupuncture or homeopathic products, without checking with your health care team.

  • DO NOT use tobacco products (such as smoking cigarettes or vaping) or drink alcohol while on treatment without talking to your health care team first. Smoking and drinking can make side effects worse and make your treatment not work as well.
DO this while on treatment

Check Mark Icon

  • DO check with your health care team before getting any vaccinations, surgery, dental work or other medical procedures.  

  • DO protect your skin from the sun. Wear a long sleeved shirt, long pants and a hat. Apply sunscreen with UVA and UVB protection and an SPF of at least 30. Your skin may be more sensitive to the sun and you could develop a bad sunburn or rash more easily.

DO NOT do this while on treatment

Stop Icon

  • DO NOT take any other medications, such as vitamins, over-the-counter (non-prescription) drugs or substances, or natural health products without checking with your health care team.

  • DO NOT start any complementary or alternative therapies, such as acupuncture or homeopathic products, without checking with your health care team.

  • DO NOT use tobacco products (such as smoking cigarettes or vaping) or drink alcohol while on treatment without talking to your health care team first. Smoking and drinking can make side effects worse and make your treatment not work as well.

Will this treatment interact with other medications or natural health products?

Yes, this medication can interact with other medications, vitamins, foods, traditional medicines and natural health products. Interactions can make this medication not work as well or cause severe side effects.

Tell your health care team about all of your:

  • prescription and over-the-counter (non-prescription) medications
  • other drugs and substances, such as cannabis/marijuana (medical or recreational)
  • natural health products such as vitamins, herbal teas, homeopathic medicines, and other supplements, or traditional medicines

Check with your health care team before starting or stopping any of them.

 

Medication Icon
Talk to your health care team BEFORE taking or using these :
  • Anti-inflammatory medications such as ibuprofen (Advil® or Motrin®), naproxen (Aleve®) or Aspirin®.
  • Over-the-counter products such as dimenhydrinate (Gravol®) 
  • Natural health products such as St. John’s Wort
  • Traditional medicines
  • Supplements such as vitamin C
  • Grapefruit juice
  • Alcoholic drinks 
  • Tobacco 
  • All other drugs or substances, such as marijuana or cannabis (medical or recreational)
What to do if you feel unwell, have pain, a headache or a fever

  • Always check your temperature to see if you have a fever before taking any medications for fever or pain (such as acetaminophen (Tylenol®) or ibuprofen (Advil®)).

    • Fever can be a sign of infection that may need treatment right away.

    • If you take these medications before you check for fever, they may lower your temperature and you may not know you have an infection.

How to check for fever:

Keep a digital (electronic) thermometer at home and take your temperature if you feel hot or unwell (for example, chills, headache, mild pain). 

  • You have a fever if your temperature taken in your mouth (oral temperature) is:

    • 38.3°C (100.9°F) or higher at any time

  •       OR

    • 38.0°C (100.4°F) or higher for at least one hour.

Medication Icon

If you do have a fever : 

  • Try to contact your health care team.  If you are not able to talk to them for advice, you MUST get emergency medical help right away.

  • Ask your health care team for the Fever pamphlet for more information.

 

If you do not have a fever but have mild symptoms such as headache or mild pain:

  • Ask your health care team about the right medication for you. Acetaminophen (Tylenol®) is a safe choice for most people.
Stop Icon

Talk to your health care team before you start taking ibuprofen (Advil®, Motrin®), naproxen (Aleve®) or ASA (Aspirin®), as they may increase your chance of bleeding or interact with your cancer treatment.

Important Icon

Talk to your health care team if you already take low dose aspirin for a medical condition (such as a heart problem). It may still be safe to take.

How will this treatment affect sex, pregnancy and breastfeeding?

Talk to your health care team about:

  • How this medication may affect your sexual health.

  • How this medication may affect your ability to have a baby, if this applies to you.


This treatment may harm an unborn baby. Tell your health care team if you or your partner are pregnant, become pregnant during treatment, or are breastfeeding.

  • If there is any chance of pregnancy happening, you and your partner together must use 2 effective forms of birth control at the same time until at least 1 month after your last treatment dose. Talk to your health care team about which birth control options are best for you.
     

  • Do not breastfeed while on this treatment.

How to safely store and handle this medication

  • Keep this medication in the original packaging at room temperature in a dry place, away from heat and light. Keep out of sight and reach of children and pets.

  • Do not throw out any unused medications at home. Bring them to your pharmacy to be thrown away safely.
     

How to safely touch oral anti-cancer medication


If you are a patient:

  • Wash your hands before and after touching your oral anti-cancer medication.

  • Swallow each pill whole. Do not crush or chew your pills.

If you are a caregiver:

  • Wear nitrile or latex gloves when touching tablets, capsules or liquids.
     

  • Wash your hands before putting on your gloves and after taking them off, even if your skin did not touch the oral anti-cancer medication.
     

  • Throw out your gloves after each use. Do not re-use gloves. 
     

  • Do not touch oral anti-cancer medications if you are pregnant or breastfeeding.

 

What to do if anti-cancer medication gets on your skin or in your eyes 


If medication gets on your skin:

  • Wash your skin with a lot of soap and water.

  • If your skin gets red or irritated, talk to your health care team.

If medication gets in your eyes:

  • Rinse your eyes with running water right away. Keep water flowing over your open eyes for at least 15 minutes.

 

What are the side effects of this treatment?

You may not have all of the side effects below. You may have side effects that are not listed.
 


Side effects and what to do When to contact doctor?
Very Common Side Effects (50 or more out of 100 people)

Abnormal cholesterol or fat levels in the blood

  • Your doctor may check your cholesterol levels regularly with a blood test.
 Contact your health care team if no improvement or if severe.

Abnormal liver lab tests (may be severe)

  • Your doctor will monitor your liver regularly with a blood test.
  • You may have yellowish skin or eyes, unusually dark pee or pain on the right side of your belly. Talk to your health care team if this happens.
     
 Contact your health care team if no improvement or if severe.

 

Side effects and what to do When to contact doctor?
Common Side Effects (25-49 out of 100 people)

Diarrhea (may be severe)

May happen during treatment, within days to weeks 


If you have diarrhea:

  • Take anti-diarrhea medication if your health care team prescribed it.
  • Avoid foods or drinks with artificial sweetener (e.g. chewing gum, “diet” drinks), coffee and alcohol, until your diarrhea has stopped.
  • Eat many small meals and snacks instead of 2 or 3 large meals.
  • Drink at least 6 to 8 cups of liquids each day. Talk to your health care team if you can’t drink 6-8 cups of liquids each day when you have diarrhea. You may need special liquids with salt and sugar, called Oral Rehydration Therapy.

​See the Diarrhea pamphlet for more information.
 

 Contact your health care team if no improvement or if severe.

Fatigue (tiredness)

  • Be active and aim to get 30 minutes of moderate exercise (you are able to talk comfortably while exercising) on most days. Check with your health care team before starting any new exercise.
  • Pace yourself, do not rush. Put off less important activities. Rest when you need to.
  • Eat well and stay hydrated by drinking at least 6 to 8 glasses of water or other liquids every day (unless your doctor told you to drink more or less).
  • Avoid driving or using machinery if you are feeling tired

See our Fatigue pamphlet for more information. 
 

 Contact your health care team if no improvement or if severe.

Cough; feeling short of breath

You may have cough and feel short of breath without any signs of infection, such as a sore throat or a stuffed nose.
 

 Contact your health care team if no improvement or if severe.

Nausea and vomiting (usually mild)

May occur in hours to days after your treatment. 


If you have nausea or vomiting:

  • Take anti-nausea medication(s) as prescribed to you by your doctor. 
  • Drink clear liquids and have small meals. Get fresh air and rest.
  • Do not eat spicy, fried foods or foods with a strong smell.
  • Limit caffeine (e.g. coffee, tea) and alcohol.
  • Contact your health care team if the prescribed anti-nausea medications are not helping to control your nausea and vomiting.

 Also see Nausea & Vomiting pamphlet for more information.
 

 Contact your health care team if no improvement or if severe.

Pains or cramps in the belly

  • If you have constipation or diarrhea it may be causing the pain in your belly.
  • If the pain is severe, gets worse or doesn’t go away, talk to your health care team about other possible causes.
     
 Contact your health care team if no improvement or if severe.

Low platelets in the blood (may be severe)

  • Watch for bleeding (such as unusual nosebleeds or bleeding from the gums) or bruising easily (this is rare).
  • Very rarely, severe symptoms can happen. If you notice black coloured stools (poo), red or pink coloured urine (pee), red or brown coloured mucus when you cough, severe headache/confusion or bleeding that will not stop, you need to talk to your health care team or go to the nearest emergency room right away.

See the Low Platelet Count pamphlet for more information.


Fever, chills, infection (may be severe)

You have a fever if your temperature taken in your mouth (oral temperature) is:

  • 38.3°C (100.9°F) or higher at any time OR
  • 38.0°C (or 100.4°F) or higher for at least one hour.

While you are getting chemotherapy treatments:

  • Keep a digital thermometer at home and take your temperature if you feel hot or unwell (for example, chills).
  • Avoid taking medications that treat a fever before you take your temperature (for example, Tylenol®, acetaminophen, Advil® or ibuprofen) as they may hide a fever.
  • Do not eat or drink anything hot or cold right before taking your temperature.
  • Wash your hands often.
  • Check with your doctor before getting any vaccines, surgeries, medical procedures or visiting your dentist.

If you have a fever, talk to your health care team or go to the closest emergency room. 

See our Neutropenia (Low white blood cell count) pamphlet for more information.

 Get emergency medical help right away.

 

 
Side effects and what to do When to contact doctor?
Less Common Side Effects (10-24 out of 100 people)

Rash

Rash may be severe in some rare cases and cause your skin to blister or peel. If this happens, get emergency medical help right away.

To prevent and treat dry skin,

  • Use skin moisturizer.
  • Protect your skin from the sun and the cold.
  • Use sunscreen with UVA and UVB protection and a SPF of at least 30.
 Contact your health care team if no improvement or if severe.

Low appetite

  • You may not feel like eating or you may lose weight.
  • Try to eat foods that you like and eat small meals throughout the day. 
  • You may need to take meal supplements to help keep your weight up.
  • Talk to your health care team if you have a low appetite.
  • See our Loss of appetite pamphlet for more information.
 Contact your health care team if no improvement or if severe.

Trouble falling asleep

  • This may be caused by one of your medications and may improve once your body gets used to the medication or when your treatment ends.
  • Talk to your doctor if this bothers you.
 Contact your health care team if no improvement or if severe.

Headache; mild joint, muscle pain

  • Take your pain medication as prescribed by your doctor.
  • You can take acetaminophen (Tylenol®) tablets as needed for mild aches and pains. Ask your doctor or pharmacist about the right dose for you.
  • Talk to your doctor or pharmacist first before taking ibuprofen (Advil®, Motrin®), naproxen (Aleve®) or aspirin. These medications may increase bleeding risk.
  • Rest often and try light exercise as it may help.
 Contact your health care team if no improvement or if severe.

Mild swelling in arms and legs; puffiness

To help prevent swelling :

  • Eat a low-salt diet.
  • Avoid tight fitting clothing.

If you have swelling in your legs, keep your feet up when sitting.

 Contact your health care team if no improvement or if severe.

Other rare, but serious side effects are possible with this treatment.

If you have any of the following, talk to your cancer health care team or get emergency medical help right away:

  • Difficulty breathing, painful cough, chest pain and/or coughing up blood
  • Symptoms of an allergic reaction (during or shortly after taking the medication) such as fever, rash, swollen lips, face or tongue, wheezing, chest and throat tightness
  • Feeling confused, have difficulty speaking, moving or problems with your balance
  • Blurred vision or loss of vision and weakness on one side of your body
  • Redness, blistering and/or peeling of large areas of the skin and/or inside of the lips, eyes, mouth, nasal passages or genitals, along with fever, chills, headache, cough, body aches or swollen glands

For more information on how to manage your symptoms ask your health care provider, or visit: https://www.cancercareontario.ca/symptoms.

Notes

May 2026 Updated/revised information sheet

The information set out in the medication information sheets, regimen information sheets, and symptom management information (for patients) contained in the Drug Formulary (the "Formulary") is intended to be used by health professionals and patients for informational purposes only. The information is not intended to cover all possible uses, directions, precautions, drug interactions or side effects of a certain drug, nor should it be used to indicate that use of a particular drug is safe, appropriate or effective for a given condition.

A patient should always consult a healthcare provider if he/she has any questions regarding the information set out in the Formulary. The information in the Formulary is not intended to act as or replace medical advice and should not be relied upon in any such regard. All uses of the Formulary are subject to clinical judgment and actual prescribing patterns may not follow the information provided in the Formulary.

Last Updated: July 21, 2026

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