Ondansetron (Zofran) vs. palonosetron (Aloxi): Side Effects, Dosage

Ondansetron (Zofran) vs. palonosetron (Aloxi): What’s the difference?

• Ondansetron and palonosetron are anti-nausea medications used to prevent nausea and vomiting caused by cancer chemotherapy and to prevent vomiting and nausea after surgery.
• Brand names for ondansetron include Zofran, Zofran ODT, and Zuplenz.
• A brand name for palonosetron is Aloxi.
• Side effects of ondansetron and palonosetron that are similar include headache, constipation, dizziness, fatigue, and abnormal heart rate and rhythm.
• Side effects of ondansetron that are different from palonosetron include feeling unwell (malaise), drowsiness, and diarrhea.
• Side effects of palonosetron that are different from ondansetron include abdominal pain and insomnia.

What are ondansetron and palonosetron?

Ondansetron is an anti-nausea medication most often used to prevent nausea and vomiting caused by cancer chemotherapy and to prevent vomiting and nausea after surgery. Chemotherapy drugs increase secretion of serotonin, which stimulates serotonin (5-HT3) receptors in the brain, causing nausea and vomiting. Ondansetron works by selectively blocking serotonin (5-HT3) receptors, reducing the effect of increased serotonin due to chemotherapy.

Palonosetron hydrochloride injection is a serotonin-3 (5-HT3) receptor antagonist indicated for prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of cancer chemotherapy and prevention of postoperative nausea and vomiting. Chemotherapy drugs produce nausea and vomiting by releasing serotonin, which then activates 5-HT3 receptors and initiates the vomiting reflex. Palonosetron selectively blocks serotonin (5-HT3) receptors, reducing the effect of increased serotonin due to chemotherapy.

What are the side effects of ondansetron and palonosetron?

Ondansetron

Side effects of ondansetron are

• headache,
• malaise,
• fatigue,
• drowsiness,
• constipation,
• dizziness, and
• diarrhea.

Some individuals may develop abnormal heart rate and rhythm.

Palonosetron

Serious allergic reactions

Palonosetron can cause allergic reactions that can sometimes be serious. Tell your doctor or nurse right away if you have any of the following symptoms of a serious allergic reaction:

• hives,
• swollen face,
• breathing trouble, or
• chest pain.

Serotonin syndrome

A possible life-threatening condition called serotonin syndrome can occur with medicines called 5-HT3 receptor antagonists, including palonosetron, especially when used with medicines used to treat depression and migraine headaches called serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs) and certain other medicines. Tell your doctor or nurse right away if you have any of the following symptoms of serotonin syndrome:

• agitation, seeing things that are not there (hallucinations), confusion, or coma,
• fast heartbeat or unusual and frequent changes in your blood pressure,
• dizziness, sweating, flushing, or fever,
• tremors, stiff muscles, muscle twitching, overactive reflexes, or loss of coordination,
• seizures,
• nausea, vomiting, or diarrhea.

Common side effects

The most common side effects of palonosetron in adults who receive the medication to help prevent nausea and vomiting that occurs with certain anti-cancer medicine (chemotherapy) include:

• headache, and
• constipation.

The most common side effects of palonosetron in adults who receive the medication to help prevent nausea and vomiting that occurs while recovering from anesthesia after surgery include:

• serious or life-threatening heart rhythm changes (QT prolongation),
• slow heartbeat,
• headache, and
• constipation.

These are not all the possible side effects. Call your doctor for medical advice about side effects.

What is the dosage of ondansetron vs. palonosetron?

Ondansetron

Dosage for adults:

• Highly nauseating chemotherapy: 24 mg orally dissolved on tongue 30 minutes prior to start of a single-day chemotherapy.
• Moderately nauseating chemotherapy: Take 8 mg tablet 30 minutes prior to chemotherapy and repeat in 8 hours, then 8 mg every 12 hours for 1 to 2 days after chemotherapy.
• Radiation-induced nausea and vomiting: Take 8 mg orally 1 to 2 hours prior to radiation and every 8 hours after first dose, as needed.
• Post-surgery nausea and vomiting: 16 mg orally 1 hour before anesthesia.

Dosage for children:

• Moderately nauseating chemotherapy (12 years and older): 8 mg orally prior to chemotherapy and repeat in 8 hours, then 8 mg every 12 hours for 1 to 2 days after chemotherapy.
• Moderately nauseating chemotherapy (4 to 11 years): 4 mg orally 30 minutes prior to chemotherapy and repeat in 4 and 8 hours after the first dose, then every 8 hours for 1 to 2 days after chemotherapy.
• Not recommended for children under 4 years old.

Palonosetron

This medication is given by injection into a vein by a health care professional usually 30 minutes before chemotherapy or right before anesthesia for surgery.

For the best possible benefit, it is important to receive each scheduled dose as directed. If you miss a dose, contact your doctor or pharmacist immediately to establish a new dosing schedule.

Chemotherapy-Induced Nausea and Vomiting

• Adults 0.25 mg as a single dose: infused over 30 seconds beginning approximately 30 minutes before the start of chemotherapy
• Pediatrics (1 month to less than 17 years) 20 micrograms per kilogram (maximum 1.5 mg) as a single dose: infused over 15 minutes beginning approximately 30 minutes before the start of chemotherapy

Postoperative Nausea and Vomiting

• The recommended adult dosage is 0.075 mg as a single intravenous dose administered over 10 seconds immediately before the induction of anesthesia.

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What drugs interact with ondansetron and palonosetron?

Ondansetron

Ondansetron and apomorphine should not be used together due to sudden lowering in blood pressure and loss of consciousness.

Phenytoin, carbamazepine, and rifampin can increase ondansetron elimination and decrease blood levels, possibly lowering the effects of ondansetron.

Dronedarone can increase blood levels of ondansetron by reducing its breakdown in the liver. This may increase side effects of ondansetron. This combination may also increase the risk of abnormal heartbeats.

Palonosetron

Before using palonosetron, report to your doctor or pharmacist all medications you are currently using (including prescription/nonprescription drugs and herbal products).

Some products that may interact with this drug include:

• anthracyclines, such as
  • doxorubicin,
  • daunorubicin,
• apomorphine.

Many drugs besides palonosetron may affect the heart rhythm (QT prolongation), including:

• amiodarone,
• dofetilide,
• pimozide,
• procainamide,
• quinidine,
• sotalol,
• macrolide
• antibiotics (such as erythromycin),
• sparfloxacin,
• among others.

Serotonin syndrome, which can be life threatening, can occur with medicines called 5-HT3 receptor antagonists, including palonosetron, especially when used with medicines used to treat depression and migraine headaches called serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs) and certain other medicines.

Are ondansetron and palonosetron safe to use while pregnant or breastfeeding?

Ondansetron

There are no adequate studies of ondansetron in pregnant women to determine its safe and effective use during pregnancy.

It is not known whether ondansetron enters breast milk; therefore, it is best to be cautious before using it in nursing mothers.

Palonosetron

It is unknown if palonosetron will harm your unborn baby. This medication should only be used when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.

It is unknown if palonosetron passes into breast milk or may harm a nursing infant. Consult your doctor before breastfeeding about the best way to feed your baby if you will receive this medication.