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Ondansetron

Medical and Pharmacy Editor:

Brand Name: Zohydro ER, Hysingla ER, Vantrela ER

Generic Name: ondansetron

Drug Class: Opioid Analgesics

What Is Ondansetron and How Does It Work?

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

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 procedure or 16 mg orally 1 hour before anesthesia; patients over 80 kg may need 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 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 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 used in adults; 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 prior to 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 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 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 procedure or 16 mg orally 1 hour before anesthesia; patients over 80 kg may need additional 4 mg intravenously

What Are Side Effects Associated with Using Ondansetron ?

Side effects of ondansetron include:

Other side effects of Ondansetron include:

Cardiac

Gastrointestinal

  • nausea
  • vomiting

Anaphylaxis

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

Hepatobiliary

General

Local reactions

  • pain, redness, and burning at injection site

Lower respiratory

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

Eye Disorders

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

Musculoskeletal and connective tissue

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

What Other Drugs Interact with Ondansetron?

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.

What Are Warnings and Precautions for Ondansetron?

Warnings

  • 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
  • Contraindications

    • Hypersensitivity
    • Coadministration with apomorphine; combination reported to cause profound low blood pressure and loss of consciousness

    Effects of Drug Abuse

    • None

    Short-Term Effects

    • 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?”

    Long-Term Effects

    • See also "What Are Side Effects Associated with Using Ondansetron?”

    Cautions

    • 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

    Pregnancy and Lactation with Ondansetron

    • Available data do not reliably inform 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 effects of ondansetron on breastfed infant or effects on milk production; the developmental and health benefits of breastfeeding should be considered along with mother's clinical need for ondansetron and any potential adverse effects on breastfed infant from therapy or from the underlying maternal condition
Reviewed on 4/6/2017


SOURCE:
Medscape. Ondansetron.
https://reference.medscape.com/drug/zofran-zuplenz-ondansetron-342052#0

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