Indications 

This medication is prescribed as monotherapy or in combination with other medications to mitigate nausea and vomiting induced by cancer treatment via chemotherapy and radiation therapy.  

This medication is used to prevent and manage postoperative nausea and vomiting. Its mechanism of action entails inhibition of serotonin, a natural substance in the body that triggers vomiting. 

Uses and Dosage 

Dosage instructions for ondansetron use are based on the patient’s medical condition and response to therapy. The usual maximum dosage for patients with severe liver issues is 8 milligrams within 24 hours. Children’s doses may depend on age and weight. Follow all directions given by your doctor. 

To prevent nausea caused by chemotherapy, take this medication orally within 30 minutes before treatment commences. To prevent nausea from radiation treatment, take this medication orally 1 to 2 hours before the start of your treatment. To prevent nausea after surgery, take ondansetron orally 1 hour before surgery. It can be taken with or without food, depending on your doctor’s instructions. However, your doctor may advise you not to eat before chemotherapy, radiation, or surgery. 

If you are taking this medication on a schedule, take it at the same time each day to avoid forgetting. Take any other doses as directed by your doctor. Ondansetron can be taken up to 3 times a day for 1 to 2 days after chemotherapy or radiation treatment. Avoid taking more medication than prescribed or taking it more often than instructed. Seek your doctor’s or pharmacist’s guidance if you have any doubts. 

Side Effects 

Allergic Reactions

Seek emergency medical attention immediately if you experience signs of an allergic reaction to Zofran, such as: 

• Hives 
• Rash 
• Fever 
• Chills 
• Difficult breathing 
• Swelling of your face, lips, tongue, or throat 

Severe Side Effects

In case you encounter any of the following side effects, call your doctor right away: 

• Severe constipation, stomach pain, or bloating 
• Headache accompanied by chest pain and severe dizziness, fainting, fast or pounding heartbeats 
• Fast or pounding heartbeats 
• Jaundice (yellowing of the skin or eyes) 
• Blurred vision or temporary vision loss, lasting from a few minutes to several hours 
• High levels of serotonin in the body, including symptoms such as:
  • Agitation
  • Hallucinations
  • Fever
  • Fast heart rate
  • Overactive reflexes
  • Nausea
  • Vomiting
  • Diarrhea
  • Loss of coordination
  • Fainting 

Common Side Effects  

• Diarrhea or constipation 
• Headache 
• Drowsiness 
• A tired feeling 

Caution 

Before taking ondansetron, inform your doctor or pharmacist if you are allergic to it, other serotonin blockers (such as granisetron), or if you have any other allergies. 

This medication may contain inactive ingredients that can cause allergic reactions or other problems, so consult your pharmacist for more information. 

Inform your doctor or pharmacist of your medical history, particularly if you have irregular heartbeat, liver disease, or stomach/intestinal issues (such as recent abdominal surgery, ileus, swelling). 

This medication may cause dizziness or drowsiness. Consuming alcohol or marijuana (cannabis) may intensify these effects. Therefore, do not operate heavy machinery, drive, or perform any activities that require alertness until you can perform them safely. 

Limit alcoholic beverages and speak with your doctor if you are using marijuana (cannabis).