Granisetron is used to prevent nausea and vomiting caused by cancer chemotherapy and radiation therapy. Granisetron is in a class of medications called 5-HT₃ receptor antagonists. It works by blocking serotonin, a natural substance in the body that causes nausea and vomiting.

Granisetron comes as a tablet to take by mouth. When taken to prevent nausea and vomiting caused by chemotherapy, granisetron is usually taken 1 hour before chemotherapy is begun. A second dose may be taken 12 hours after the first dose depending on the strength. When taken to prevent nausea and vomiting caused by radiation, granisetron is usually taken within 1 hour before treatment. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take granisetron exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking granisetron,

• tell your doctor and pharmacist if you are allergic to granisetron, alosetron (Lotronex), dolasetron (Anzemet), ondansetron (Zofran, Zuplenz), palonosetron (Aloxi, in Akynzeo), any other medications, or any of the ingredients in granisetron tablets. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: fentanyl (Abstral, Actiq, Duragesic, Fentora, Lazanda, Onsolis, Subsys); ketoconazole (Nizoral), lithium (Lithobid); medications to treat migraines such as almotriptan (Axert), eletriptan (Relpax), frovatriptan (Frova), naratriptan (Amerge), rizatriptan (Maxalt), sumatriptan (Imitrex), and zolmitriptan (Zomig); methylene blue; mirtazapine (Remeron); monoamine oxidase (MAO) inhibitors including isocarboxazid (Marplan), linezolid (Zyvox), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate); phenobarbital; selective serotonin reuptake inhibitors (SSRIs) such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem, in Symbyax), fluvoxamine (Luvox), paroxetine (Brisdelle, Paxil, Pexeva), and sertraline (Zoloft); and tramadol (Conzip, Ultram, in Ultracet). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking granisetron, call your doctor.

Unless your doctor tells you otherwise, continue your normal diet.

Granisetron should only be taken before chemotherapy or radiation therapy, as instructed by your doctor. It should not be taken on a regularly scheduled basis.

Granisetron may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• headache
• stomach pain
• heartburn
• constipation
• difficulty falling asleep or staying asleep

Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately or seek emergency medical treatment:

• hives
• rash
• itching
• difficulty breathing or swallowing
• shortness of breath
• dizziness, light-headedness, or fainting
• fast, slow or irregular heartbeat
• agitation
• hallucinations (seeing things or hearing voices that do not exist)
• fever
• flushing
• excessive sweating
• confusion
• nausea, vomiting, or diarrhea
• loss of coordination
• stiff or twitching muscles
• seizures
• coma (loss of consciousness)

Granisetron may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

• headache

Keep all appointments with your doctor.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

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