Class Name(s):

• 56:22.20 5-HT3 Receptor Antagonists

Pronunciation:

• (on dan' se tron)

Brand Name(s):

• Zofran^® Injection; also available generically

WHY is this medicine prescribed?

Ondansetron injection is used to prevent nausea and vomiting caused by cancer chemotherapy and surgery. Ondansetron is in a class of medications called serotonin 5-HT₃ receptor antagonists. It works by blocking the action of serotonin, a natural substance that may cause nausea and vomiting.

HOW should this medicine be used?

Ondansetron comes as a solution (liquid) to be injected intravenously (into a vein) or intramuscularly (into a muscle) by a health care provider in a hospital or clinic. When ondansetron is used to prevent nausea and vomiting caused by chemotherapy, it is usually given 30 minutes before the start of chemotherapy. Additional doses may be given 4 hours after the first dose of ondansetron and 8 hours after the first dose of ondansetron, if needed. When ondansetron is used to prevent nausea and vomiting caused by surgery, it is usually given just before the surgery. Ondansetron is also sometimes given after surgery to patients who are experiencing nausea and vomiting and who did not receive ondansetron before surgery.

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

What SPECIAL PRECAUTIONS should I follow?

Before using ondansetron,

• tell your doctor and pharmacist if you are allergic to ondansetron, alosetron (Lotronex), dolasetron (Anzemet), granisetron (Kytril), palonosetron (Aloxi), or any other medications: or any of the ingredients in ondansetron injection. Ask your pharmacist for a list of the ingredients.
• tell your doctor if you are receiving apomorphine (Apokyn). Your doctor will probably tell you not to use ondansetron if you are receiving this medication.
• some medications should not be taken with ondansetron injection. Other medications may cause dosing changes or extra monitoring when taken with ondansetron injection. Make sure you have discussed any medications you are currently taking or plan to take before using ondansetron injection with your doctor and pharmacist. Before starting, stopping, or changing any medications while using ondansetron injection, please get the advice of your doctor or pharmacis;.
• 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), or another type of irregular heart beat or heart rhythm problem, or if you have or have ever had low levels of magnesium or potassium in your blood, heart failure (HF; condition in which the heart cannot pump enough blood to other parts of the body), or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while receiving ondansetron, call your doctor.

What SPECIAL DIETARY instructions should I follow?

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

What SIDE EFFECTS can this medicine cause?

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

• headache
• constipation
• drowsiness
• feeling cold or chills
• pain, burning, numbness, or tingling in the hand or feet
• fever
• injection site pain, redness, swelling, warmth, or burning

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

• rash
• hives
• itching
• swelling of the eyes, face, lips, tongue, throat, hands, feet, ankles, or lower legs
• hoarseness
• difficulty breathing or swallowing
• chest pain
• shortness of breath
• dizziness, light-headedness, or fainting
• fast, slow or irregular heartbeat
• blurred vision or vision loss
• lightheadedness
• agitation
• hallucinations (seeing things or hearing voices that do not exist)
• fever
• excessive sweating
• confusion
• nausea, vomiting, or diarrhea
• loss of coordination
• stiff or twitching muscles
• seizures
• coma (loss of consciousness)

Ondansetron may cause other side effects. Call your doctor if you have any unusual problems while you are 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).

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://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:

• sudden loss of vision for a short time
• dizziness or lightheadedness
• fainting
• constipation
• irregular heart beat

What should I know about STORAGE and DISPOSAL of this medication?

This medication will be stored in the hospital or clinic.

What OTHER INFORMATION should I know?

Keep all appointments with your doctor.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: January 15, 2015.