Ondansetron

Ondansetron is used alone or with other medications to prevent nausea and vomiting caused by cancer drug treatment (chemotherapy), radiation treatment, or drugs used to put you to sleep before surgery. Ondansetron works by blocking one of the body's natural substances (serotonin) that causes vomiting.

Ondansetron is available under the following different brand names: Zofran, Zofran ODT, and Zuplenz.

Dosages of Ondansetron

Adult and pediatric dosages

Injectable solution

• 2 mg/ml

Tablet

• 4 mg
• 8 mg
• 24 mg (adult only)

Oral solution

• 4 mg/ml

Oral soluble film

• 4 mg
• 8 mg

Orally disintegrating tablets

• 4 mg
• 8 mg

Dosage Considerations -- Should Be Given As Follows:

Adult dosage considerations

Postoperative Nausea and Vomiting

Prophylaxis

• 4 mg intravenously/intramuscular immediately before anesthesia or after the procedure or 16 mg orally 1 hour before anesthesia; patients over 80 kg may need an additional 4 mg intravenously

Radiation-Induced Nausea and Vomiting

Prophylaxis

• Total body radiation therapy: 8 mg orally 1-2 hours before radiation therapy; administered each day
• Single high-dose fraction therapy to the abdomen: 8 mg orally 1-2 hours before radiation therapy; administer subsequent doses every 8 hours after first dose 1-2 days after completion of therapy
• Daily fractions to the abdomen: Administer 8 mg orally 1-2 hours before radiotherapy; administer subsequent doses every 8 hr after first dose each day radiotherapy is given

Dosage Modifications

• Renal impairment: Dose adjustment not necessary
• Severe hepatic impairment (Child-Pugh score equal to 10): Not to exceed 8 mg/day

Cholestatic Pruritus (Off-label)

• 8 mg divided every 12 hours or 8 mg every 8-12 hours orally for 7 days up to 5 months
• Alternatively, 4-8 mg intermittent short-term intravenous dosing is used in adults; a single dose of 4 mg single dose used in pregnancy

Uremic Pruritus (Off-label)

• 8 mg divided every 12 hours or 8 mg every 8 to 12 hours orally for 14 days up to 5 months

Spinal Opioid-Induced Pruritus (Off-label)

Prophylaxis

• 4-8 mg intravenously 20-30 min before spinal opioid therapy; may repeat dosing at 12, 24, 36, 48 hours after spinal opioid dosing

Treatment

• 4-8 mg intravenously

Rosacea (Off-label)

• 4-8 mg orally every 12 hours for up to 3 weeks
• Alternatively, 12 mg IV daily for 4 days

Hyperemesis Gravidarum

• 10 mg IV every 8 hours as needed

Pediatric dosage considerations

Chemotherapy-Induced Nausea and Vomiting

Prophylaxis, Oral Dosing

• Children under 4 years old: Safety and efficacy not established
• Children 4-12 years: 4 mg started 30 min before chemotherapy, then 4 and 8 hours after the first dose, then every 8 hours for 1-2 days after chemotherapy
• Children over 12 years: 8 mg started 30 min before chemotherapy, then every 12 hours for 1-2 days after chemotherapy or single dose of 24 mg

IV Dosing

• Children under 6 months: Safety and efficacy not established
• Children 6 months or older: 0.15 mg/kg over 15 min administered 30 min before chemotherapy, then repeated 4 and 8 hours after the first dose; not to exceed 16 mg/dose (32 mg no longer recommended because of increased risk of QT prolongation)

Postoperative Nausea and Vomiting

Prophylaxis

• 1 month-12 years
• Under 40 kg, 0.1 mg/kg intravenously
• Over 40 kg, 4 mg intravenously
• Under 12 years
• 4 mg intravenously/intramuscularly immediately before anesthesia or after the procedure or 16 mg orally 1 hour before anesthesia; patients over 80 kg may need an additional 4 mg intravenously

Side effects of ondansetron include:

• headache
• malaise/fatigue
• constipation
• poor oxygenation
• drowsiness
• diarrhea
• dizziness
• fever
• gynecologic disorder
• anxiety
• urinary retention
• severe itching
• injection-site pain
• numbness and tingling
• cold sensation
• elevated liver function test results

Other side effects of Ondansetron include:

Cardiac

• heart rate irregularities (including ventricular and supraventricular tachycardia, premature ventricular contractions, and atrial fibrillation)
• slow heart rate
• electrocardiographic alterations (including second-degree heart block, QT/QTc interval prolongation, and ST segment depression)
• palpitations
• fainting (rarely and predominantly with intravenous ondansetron)
• transient ECG changes including QT/QTc interval prolongation have been reported

Gastrointestinal

• nausea
• vomiting

Anaphylaxis

• ECG alterations: heartbeat irregularities; prolongation of PR, QRS, and QT intervals

Hepatobiliary

• specific hepatic enzyme abnormalities
• hepatic necrosis
• abnormal hepatic function

General

• flushing
• rare cases of hypersensitivity reactions, sometimes severe (acute allergic reactions, rapid swelling, difficulty breathing, cardiopulmonary arrest, low blood pressure, laryngeal edema, laryngospasm, shock, shortness of breath, or stridor)

Local reactions

• pain, redness, and burning at the injection site

Lower respiratory

• hiccups

Neurological

• involuntary intermittent or sustained deviation of the eyes, appearing alone, as well as with other dystonic reactions; transient dizziness during or shortly after intravenous infusion

Skin and subcutaneous tissue

• hives
• Stevens-Johnson syndrome
• toxic epidermal necrolysis

Eye Disorders

• Transient blindness (predominantly during IV administration) was reported to resolve within a few minutes up to 48 hr;
• transient blurred vision

Musculoskeletal and connective tissue

• joint pain

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

Severe Interactions of Ondansetron include:

• apomorphine
• dronedarone

Ondansetron has serious interactions with at least 119 different drugs.

Ondansetron has moderate interactions with at least 53 different drugs.

Ondansetron has minor interactions with at least 28 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

Warnings

Contraindications

• N/A

Effects of Drug Abuse

• N/A

Short-Term Effects

• N/A

Long-Term Effects

• N/A

Cautions

Pregnancy and Lactation with Ondansetron

• This medication contains ondansetron. Do not take Zofran, Zofran ODT, or Zuplenz if you are allergic to ondansetron or any ingredients contained in this drug
• Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately
  • Hypersensitivity
  • Coadministration with apomorphine; combination reported to cause profound low blood pressure and loss of consciousness
  • None
  • Ondansetron may mask progressive ileus or gastric distention in patients who are undergoing abdominal surgery or experiencing chemotherapy-induced nausea and vomiting; monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction
  • See also "What Are Side Effects Associated with Using Ondansetron?”
  • See also "What Are Side Effects Associated with Using Ondansetron?”
  • Hypersensitivity reactions including anaphylaxis and bronchospasm may occur: discontinue therapy if suspected; monitor and treat promptly per standard of care until signs and symptoms resolve
  • Reduce dose with severe hepatic impairment
  • Use according to schedule, not as needed
  • Ondansetron may mask progressive ileus or gastric distention in patients who are undergoing abdominal surgery or experiencing chemotherapy-induced nausea and vomiting; monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction
  • Ondansetron is not a drug that stimulates gastric or intestinal peristalsis; should not be used instead of nasogastric suction
  • Serotonin syndrome reported with 5-HT3 receptor antagonists alone but particularly with concomitant use of serotonergic drugs including SSRIs, SNRIs, MAO inhibitors, lithium, tramadol, methylene blue IV, and mirtazapine; if concomitant use with other serotonergic drugs is clinically warranted, patients should be made aware of potential increased risk for serotonin syndrome
  • Cross-sensitivity among selective serotonin antagonists may occur
  • Zofran ODT contains phenylalanine (caution for phenylketonurics)
  • Dose-dependent QT prolongation; avoid in patients with congenital long QT syndrome; ECG monitoring recommended in patients who have electrolyte abnormalities, chronic heart failure, or bradyarrhythmias or who are also receiving other medications that cause QT prolongation
  • Available data do not reliably in form of association with adverse fetal outcomes when ondansetron is used during pregnancy; published epidemiological studies on the association between ondansetron and fetal outcomes have reported inconsistent findings and have important methodological limitations hindering interpretation
  • It is not known whether ondansetron is present in human milk; there are no data on the effects of ondansetron on breastfed infants or effects on milk production; the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for ondansetron and any potential adverse effects on the breastfed infant from therapy or the underlying maternal condition