What is the recommended dosage and administration of ondansetron (serotonin 5-HT3 receptor antagonist) for preventing nausea and vomiting?

From the Guidelines

Ondansetron is typically administered at 4-8 mg orally or intravenously every 8 hours for prevention of nausea and vomiting. For chemotherapy-induced nausea, a single 8-24 mg oral dose is given 30 minutes before treatment, while for postoperative nausea, 4 mg IV is recommended before anesthesia induction. For ongoing treatment, the oral dosing can continue for 1-2 days after the nausea-inducing event has passed. Ondansetron works by blocking serotonin receptors in the chemoreceptor trigger zone and gastrointestinal tract, preventing the vomiting reflex. Patients should be aware of potential side effects including headache, constipation, and QT interval prolongation. Dose adjustments may be necessary for patients with hepatic impairment, and the medication should be used cautiously in patients with cardiac conditions or electrolyte abnormalities. The medication can be taken with or without food, and the orally disintegrating tablets should be placed on the tongue rather than swallowed whole.

Some key points to consider when administering ondansetron include:

• The intravenous dose of ondansetron is 8 mg, as noted in the study by 1 and 1.
• Ondansetron is usually given once daily, but for delayed emesis, corticosteroids are given two times daily, as stated in the study by 1.
• The study by 1 found that combining palonosetron, aprepitant, and dexamethasone was effective for preventing both acute and delayed emesis and nausea when using various chemotherapeutic regimens.
• The medication should be used cautiously in patients with cardiac conditions or electrolyte abnormalities, as noted in the example answer.

It's also important to consider the following:

• Aprepitant is metabolized via CYP3A4 and various drugs could be influenced, as stated in the study by 1.
• When corticosteroids are combined with aprepitant, the dose of oral/i.v. corticosteroids should be reduced to 50%/75%, as noted in the study by 1.
• The study by 1 found that the addition of aprepitant to a 5-HT3 receptor antagonist and dexamethasone was beneficial in improving complete response rates for patients receiving concomitant emetogenic therapy with doxorubicin and/or cyclophosphamide, along with high-dose cisplatin therapy.

Overall, ondansetron is a effective medication for preventing nausea and vomiting, but it's essential to consider the individual patient's needs and potential interactions with other medications.

From the FDA Drug Label

2 DOSAGE & ADMINISTRATION

2.1 Prevention of Nausea and Vomiting Associated with Initial and Repeat Courses of Emetogenic Chemotherapy The recommended dosage for adult and pediatric patients 6 months of age and older for prevention of nausea and vomiting associated with emetogenic chemotherapy is 0.15-mg/kg per dose for 3 doses (maximum of 16 mg per dose). Infuse intravenously over 15 minutes beginning 30 minutes before the start of emetogenic chemotherapy and then repeat 4 and 8 hours after the first dose.

The recommended dosage of ondansetron for preventing nausea and vomiting associated with emetogenic chemotherapy is 0.15-mg/kg per dose for 3 doses, with a maximum of 16 mg per dose. The recommended administration is to infuse intravenously over 15 minutes, starting 30 minutes before the start of emetogenic chemotherapy, and then repeat 4 and 8 hours after the first dose 2.

• Key points:
  • Dose: 0.15-mg/kg per dose
  • Maximum dose: 16 mg per dose
  • Administration: Infuse intravenously over 15 minutes
  • Timing: Start 30 minutes before emetogenic chemotherapy, and repeat 4 and 8 hours after the first dose

From the Research

Recommended Dosage and Administration of Ondansetron

The recommended dosage and administration of ondansetron for preventing nausea and vomiting vary depending on the specific context, such as the type of chemotherapy or radiation treatment being used.

• For patients receiving chemotherapy without cisplatin, a dose of 4 mg IV and 4 mg orally immediately prior to chemotherapy, followed by 8 mg orally after six and 12 hours, and then 8 mg orally eight hourly during days 2-5, has been shown to be effective 3.
• For patients receiving cisplatin chemotherapy, a dose of 8 mg IV immediately prior to chemotherapy, followed by an infusion of 1 mg/hr for 8 hr, with 8 mg orally at the end of the infusion, and then 8 mg orally eight hourly during days 2-6, has been used 3.
• A dose of 8 mg twice daily for 3 days has also been shown to be effective in preventing nausea and vomiting associated with moderately emetogenic cancer chemotherapy 4.
• Intravenous ondansetron 0.15 mg/kg every 4 hours for three doses has been compared to intravenous metoclopramide in the prevention of nausea and vomiting associated with high-dose cisplatin chemotherapy, with ondansetron showing higher efficacy and fewer adverse events 5.

Safety Considerations

It is essential to consider the potential risks associated with ondansetron, particularly the risk of QT interval prolongation, which can increase the risk of torsade de pointes 6.

• The US Food and Drug Administration (FDA) has issued a warning for ondansetron due to this potential risk, particularly at doses of 32 mg IV or higher.
• However, lower doses of ondansetron, such as those used for preventing nausea and vomiting in radiation treatment or postoperatively, may be safe, although further clarification is needed from the FDA 6.