ONDANSETRON (on DAN se tron) prevents nausea and vomiting from chemotherapy, radiation, or surgery. It works by blocking substances in the body that may cause nausea or vomiting. It belongs to a group of medications called antiemetics.

Take this medication by mouth with a glass of water. Follow the directions on your prescription label. Take your doses at regular intervals. Do not take your medication more often than directed.

Talk to your care team regarding the use of this medication in children. Special care may be needed.

Side effects that you should report to your care team as soon as possible:

• Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
• Bowel blockage—stomach cramping, unable to have a bowel movement or pass gas, loss of appetite, vomiting
• Chest pain (angina)—pain, pressure, or tightness in the chest, neck, back, or arms
• Heart rhythm changes—fast or irregular heartbeat, dizziness, feeling faint or lightheaded, chest pain, trouble breathing
• Irritability, confusion, fast or irregular heartbeat, muscle stiffness, twitching muscles, sweating, high fever, seizure, chills, vomiting, diarrhea, which may be signs of serotonin syndrome

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

• Constipation
• Diarrhea
• General discomfort and fatigue
• Headache

Keep out of the reach of children and pets.

Store between 2 and 30 degrees C (36 and 86 degrees F). Throw away any unused medication after the expiration date.

They need to know if you have any of these conditions:

• Heart disease
• History of irregular heartbeat
• Liver disease
• Low levels of magnesium or potassium in the blood
• An unusual or allergic reaction to ondansetron, granisetron, other medications, foods, dyes, or preservatives
• Pregnant or trying to get pregnant
• Breast-feeding

Do not take this medication with any of the following:

• Apomorphine
• Certain medications for fungal infections like fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole
• Cisapride
• Dronedarone
• Pimozide
• Thioridazine

This medication may also interact with the following:

• Carbamazepine
• Certain medications for depression, anxiety, or psychotic disturbances
• Fentanyl
• Linezolid
• MAOIs like Carbex, Eldepryl, Marplan, Nardil, and Parnate
• Methylene blue (injected into a vein)
• Other medications that prolong the QT interval (cause an abnormal heart rhythm) like dofetilide, ziprasidone
• Phenytoin
• Rifampicin
• Tramadol

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

Check with your care team right away if you have any sign of an allergic reaction.