What is ondansetron hydrochloride (Zofran) used for?

• Prevention of nausea and vomiting due to cancer chemotherapy 
• Prevention of nausea and vomiting due to radiation therapy
• Prevention of nausea and vomiting after surgery

How does ondansetron hydrochloride (Zofran) work?

Ondansetron is a 5-HT3 receptor antagonist; it works by blocking one of the body’s natural substances - serotonin. Serotonin can trigger nausea and vomiting. By blocking serotonin, ondansetron prevents such side effects. 

What is the dosage of ondansetron hydrochloride (Zofran)?

Ondansetron dosage must be adjusted for those with severe hepatic impairment; the usual maximum dose for ondansetron is 8 mg every 24 hours. 

No dose adjustment is necessary for renal impairment.

Typical adult dosage of ondansetron:

Prevention of severe nausea and vomiting from chemotherapy:

• A single 24-mg dose given 30 minutes before the start of single-day cancer chemotherapy with severe nausea and vomiting.

Prevention of moderate nausea and vomiting from chemotherapy:

• 8 mg administered 30 minutes before the start of cancer chemotherapy; Subsequent doses of 8 mg can be given twice daily (every 12 hours) for 1 to 2 days after completion of chemotherapy.

Radiation:

• 8 mg administered 1 to 2 hours before each radiotherapy session each day
• Depending on the type of radiation, you can administer subsequent doses of 8 mg every 8 hours after the first dose for 1 to 2 days after completion of radiation. 

Postoperative nausea (after surgery):

• 16 mg administered 1 hour before induction of general anesthesia such as barbiturate, spinal opioid therapy, or nitrous oxide.

Typical pediatric dosage of ondansetron:

Prevention of moderate nausea and vomiting from chemotherapy:

• 12 to 17 years of age: 8 mg given before the start of chemotherapy, with a subsequent 8 mg dose given 8 hours after the first dose - a total of 2 doses; then give 8 mg twice daily (every 12 hours) for 1 to 2 days after completion of chemotherapy.
• 4 to 11 years of age: 4 mg given 30 minutes before the start of chemotherapy, with a subsequent 4 mg dose given 4 and 8 hours after the first dose - a total of 3 doses; then administer 4 mg three times daily (every 8 hours) for 1 to 2 days after completion of chemotherapy.
• Dosage for pediatric patients may also be based on weight.