Granisetron immediate-release injection is used to prevent nausea and vomiting caused by cancer chemotherapy and to prevent and treat nausea and vomiting that may occur after surgery. Granisetron extended-release (long-acting) injection is used with other medications to prevent nausea and vomiting caused by cancer chemotherapy that may occur immediately or several days after receiving chemotherapy medications. 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 immediate-release injection comes as a solution (liquid) to be injected intravenously (into a vein) and granisetron extended-release injection comes as a liquid to be injected subcutaneously (under the skin). To prevent nausea and vomiting caused by cancer chemotherapy, granisetron immediate-release and extended-release injection(s) are usually given by a healthcare provider in a hospital or clinic within 30 minutes before the start of chemotherapy. To prevent nausea and vomiting caused by surgery, granisetron immediate-release is usually given during surgery. To treat nausea and vomiting caused by surgery, granisetron is given as soon as nausea and vomiting occurs.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

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

Before using granisetron injection,

• 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 injection. 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 or plan to take. Be sure to mention any of the following: amiodarone (Cordarone, Nexterone, Pacerone); azithromycin (Zithromax), chlorpromazine, citalopram (Celexa); clarithromycin (Biaxin, in Prevpac); erythromycin (E.E.S., ERYC, Erythrocin, others); fentanyl (Abstral, Actiq, Duragesic, Fentora, Lazanda, Subsys); ketoconazole (Nizoral); lithium (Lithobid); medications for heart problems; medications to treat migraines such as almotriptan (Axert), eletriptan (Relpax), frovatriptan (Frova), naratriptan (Amerge), rizatriptan (Maxalt), sumatriptan (Imitrex, in Treximet), and zolmitriptan (Zomig); mirtazapine (Remeron); monoamine oxidase (MAO) inhibitors including isocarboxazid (Marplan), methylene blue; linezolid (Zyvox), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate); moxifloxacin (Avelox); pimozide (Orap); phenobarbital; selective serotonin reuptake inhibitors (SSRIs) such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem, in Symbyax, others), fluvoxamine (Luvox), paroxetine (Brisdelle, Paxil, Pexeva), and sertraline (Zoloft); serotonin–norepinephrine reuptake inhibitors (SNRI) medications desvenlafaxine (Khedezla, Pristiq), duloxetine (Cymbalta), levomilnacipran (Fetzima), and venlafaxine; sotalol (Betapace, Sorine); thioridazine; and tramadol (Conzip, Ultram, in Ultracet). If you are receiving the extended-release injection, also tell your doctor if you are taking anticoagulants (‘blood thinners’) such as warfarin (Coumadin, Jantoven); antiplatelet medications such as cilostazol, clopidogrel (Plavix), dipyridamole (Persantine, in Aggrenox), prasugrel (Effient), or ticlopidine. Your doctor may need to change the doses of your medications or monitor you more carefully for side effects. Many other medications may also interact with granisetron, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
• Tell your doctor if you have recently had stomach surgery or have constipation. Also, tell your doctor if you or anyone in your family has or has ever had long QT syndrome (condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death), another type of irregular heartbeat or heart rhythm problem, electrolyte imbalance, or kidney or heart disease.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while using granisetron injection, call your doctor.

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

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

• Headache
• 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
• Flushing
• Itching
• Difficulty breathing or swallowing
• Shortness of breath
• Swelling of the eyes, face, mouth, tongue, or throat
• Chest pain
• Injection site redness, swelling, or warmth with or without fever (for the extended-release injection)
• Injection site bleeding, bruising, or pain (for the extended-release injection)
• Stomach-area pain or swelling
• Dizziness, lightheadedness, and fainting
• Changes in heartbeat
• Agitation, hallucinations (seeing things or hearing voices that do not exist). changes in mental status, or coma (loss of consciousness)
• Tremors, loss of coordination, or stiff or twitching muscles
• Fever
• Excessive sweating
• Confusion
• Nausea, vomiting, and diarrhea
• Seizures

Granisetron injection may cause other side effects. Call your doctor if you have any unusual problems while using 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).

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.

Before having any laboratory test (especially those that involve methylene blue), tell your doctor and the laboratory personnel that you are receiving granisetron injection.

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.