Ondansetron is one of the most commonly prescribed medications for the treatment of nausea and vomiting. Developed in the 1980s, Ondansetron has an excellent history and reputation as an antiemetic drug – medications that fight against nausea and vomiting.
It is used to relieve nausea from surgical anesthetics, chemotherapy, and radiation treatments. Recent studies have shown it to be effective and safe for morning sickness. Although it is not yet FDA-approved for this use, it is still commonly prescribed. This article dives into how ondansetron works, its use, side effects, and general safety.
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Understanding Ondansetron
Also known as Zofran, ondansetron blocks serotonin 5-HT3 receptors (figure 1), especially in the vagus nerve (figure 2). In other words, this medication stops the brain signals that make a person feel nauseated and need to vomit.
While safe and effective, ondansetron interacts with many other drugs, and patients should review their complete medication and supplement list with their physician before taking this medication.
Additionally, serotonin is a key chemical in the control of depression and mood disorders. Since Ondansetron blocks the reuptake of serotonin, it requires caution when given to patients with serotonin and other neurotransmitter related conditions. Odanestron blocks serotonin 5-HT3 receptors which act on histamine and can benefit those with histamine intolerance.
Dosage and Administration
While ondansetron is usually given in hospitals intravenously (IV), it is usually taken orally (as a tablet) at home. For home use, the standard doses depend on age and indication (why the medication is being used).
Oral dosage recommendations are:
For prevention of moderate nausea and vomiting after chemotherapy treatment:
- Adults and children 12 years of age and older:
- Eight (8) mg taken 30 minutes before starting cancer treatment.
- Eight (8) mg dose eight hours later
- Eight (8) mg every 12 hours for two days
- Children 4 to 11 years of age:
- Four (4) mg taken 30 minutes before starting cancer treatment
- Four (4) mg dose four-to-eight hours after the first dose
- Four (4) mg every eight hours for two days.
- Children younger than 4 years must have a unique dose determined by a doctor.
For prevention of severe nausea and vomiting after chemotherapy treatment:
- Adults, teenagers, and children 12 years of age should take one (1) 24 mg tablet 30 minutes before starting cancer treatment.
- Children younger than 12 years of age must have a unique dose determined by a doctor
For prevention of nausea and vomiting after radiation treatment:
- Adults
- Eight (8) mg one-to-two hours before radiation treatment.
- Eight (8) mg every eight hours
- Children must have a unique dose determined by a doctor
For prevention of nausea and vomiting after surgery:
- Adults should take 16 milligrams (mg) one hour before anesthesia is given
- Children must have a unique dose determined by a doctor
At home, adults can take 8 mg of ondansetron as needed, to a maximum of three doses in a 24-hour period to relieve severe nausea and vomiting.
Safety Profile - Contraindications
While considered a very safe medication, there are risks for some patients with already-existing diseases and disorders. Ondansetron is contraindicated for those with:
- Long QT Syndrome: a rare heart rhythm disorder
- Liver Disease
- Phenylketonuria (PKU): a rare disorder that is diagnosed in early infancy
- Congestive Heart Failure (CHF)
Side Effects
Like all pharmaceuticals, ondansetron produces side effects that patients should be aware of before taking this drug. Those side effects are:
Common Side Effects:
Rare Side Effects:
Rare and Medically Serious Side Effects:
- Prolonged QT: This is a dangerous heart rhythm with fast, chaotic heartbeats that can be life-threatening
- Serotonin Syndrome: A dangerous disorder marked by shivering, muscle twitching, seizures, abnormal heart rhythms, and loss of consciousness
- Jaundice: A liver issue causing the skin and eyes to appear yellow in color
Any serious side effects should be immediately reported to the prescribing physician.
Alternatives to Ondansetron
For patients in whom ondansetron is contraindicated, alternatives include:
- Metoclopramide - It is primarily used for reflux GERD, but also works well for general nausea.
- Prochlorperazine - Although it is contraindicated in those with a psychological disorder.
- Antihistamines - Ondansetron is also an antihistamine. While not as effective, other antihistamines can help control nausea.
- Acupressure - This can be an effective, non-pharmaceutical way to treat nausea.
- Dietary changes - Can effectively manage both short- and long-term nausea.
Frequently Asked Questions about Ondansetron
How quickly does ondansetron work? It usually begins to work within 30 minutes, although it may take up to two hours for full effect.
Is ondansetron safe for long-term use? Yes. This medication is safe for extended use.
Is ondansetron addictive? No. This drug is not considered addictive
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Key Takeaways
- Ondansetron is one of the safest and most commonly prescribed medications for nausea and vomiting.
- It is often used for the prevention and treatment of nausea attributed to chemotherapy treatments and surgical anesthesia,
- It is safe for use in adults, children, and pregnant women.
- It can safely be used long-term.
- Ondansetron works on serotonin receptors, so it can affect mood and depression levels
- Common side effects include nausea, diarrhea, and headache.
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