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

Granisetron belongs to the class of medications called 5-HT3 receptor antagonists. This medication is used to prevent nausea and vomiting associated with particular types of cancer chemotherapy and radiation therapy. It works by reducing the effects of a naturally-occurring chemical in the body called serotonin, which causes nausea and vomiting.

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?

Each mL of sterile injectable solution contains granisetron 1 mg (as hydrochloride). Nonmedicinal ingredients: citric acid (monohydrate), hydrochloric acid and/or sodium hydroxide (to adjust pH), methylparaben and propylparaben (as preservatives), sodium chloride, and water for injection.

How should I use this medication?

Chemotherapy: The recommended adult dose of granisetron is 2 mg on the day of chemotherapy. This can be taken as one dose (2 mg) one hour before chemotherapy, or as 2 doses of 1 mg with the first dose one hour before chemotherapy and the second dose 12 hours after chemotherapy.

Radiation: The recommended adult dose of granisetron is 2 tablets (2 mg) taken one hour before radiation treatment.

Granisetron can be given intravenously (in the vein) as an injection if you are unable to swallow or are vomiting too much. In this case, the dose is based on body weight. The recommended adult dose is calculated as 10 µg per kilogram of body weight and is given within 30 minutes of starting chemotherapy. The intravenous form of this medication will be prepared and given to you by a health care provider in a clinic or hospital setting.

Many things can affect the dose of 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 above, 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.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

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 granisetron if you:

  • are allergic to granisetron or any ingredients of the medication
  • are taking the medication apomorphine

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.

  • abdominal pain
  • constipation
  • diarrhea
  • dizziness
  • drowsiness
  • headache
  • unusual tiredness or weakness

Although most of the 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:

  • signs of heart problems such as palpitations (fast, pounding, or irregular heartbeat), chest pain, dizziness, or fainting
  • shortness of breath
  • skin rash, hives, and itching

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

  • signs of an allergic reaction such as feeling of low blood pressure, skin lumps or hives, swelling of the mouth or airway
  • symptoms of serotonin syndrome (e.g., agitation, confusion, mood changes, decreased coordination, hallucinations, fever, sweating, muscle shakes, loss of coordination)

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.


May 15, 2014

Health Canada has issued new restrictions concerning the use of Kytril (granisetron). To read the full Health Canada Advisory, visit Health Canada's web site at

Drowsiness/reduced alertness: There have been occasional reports of drowsiness by people who have taken granisetron. Avoid operating motor vehicles or doing other potentially hazardous activities until you determine the how this medication effects you.

Heart rhythm: Granisetron, like other medications in the same family, can cause changes to the normal rhythm of the heart, including an irregular heartbeat called QT prolongation. QT prolongation is a serious life-threatening condition that can cause fainting, seizures, and sudden death. If you are at risk for heart rhythm problems (e.g., people with heart failure, angina, low potassium or magnesium levels), 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.

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.

Serotonin Syndrome: Severe reactions are possible when granisetron is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, medications used to treat depression.

If you are taking antidepressants, 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.

If you experience symptoms of a reaction, such as muscle rigidity and spasms, difficulty moving, changes in mental state including delirium and agitation, get immediate medical attention. Coma and death are possible.

Pregnancy: The safety of granisetron for use by pregnant women has not been established. This medication is not recommended for use during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if granisetron passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of granisetron have not been established for children or adolescents under 18 years of age. Its use by this age group is not recommended.

What other drugs could interact with this medication?

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

  • alfuzosin
  • amantadine
  • amiodarone
  • antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
  • antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
  • apomorphine
  • "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
  • bosutinib
  • chloral hydrate
  • chloroquine
  • cisapride
  • dabrafenib
  • dasatinib
  • disopyramide
  • domperidone
  • dronedarone
  • famotidine
  • flecainide
  • formoterol
  • galantamine
  • indapamide
  • lapatinib
  • lithium
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • maprotiline
  • mefloquine
  • methadone
  • mifepristone
  • nilotinib
  • octreotide
  • paliperidone
  • pazopanib
  • pentamidine
  • pimozide
  • procainamide
  • propafenone
  • quinidine
  • quinine
  • quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
  • ritonavir
  • romidepsin
  • saquinavir
  • selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
  • serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
  • sotalol
  • sulfamethoxazole
  • sunitinib
  • tacrolimus
  • tamoxifen
  • tapentadol
  • tetrabenazine
  • thioridazine
  • tramadol
  • trazodone
  • trimethoprim
  • tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
  • vandetanib
  • vardenafil
  • vemurafenib
  • venlafaxine

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.