From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Ondansetron can be administered intramuscularly (IM) at a dose of 4-8 mg every 8-12 hours as needed (PRN) for nausea and vomiting. For most adult patients, 4 mg is an appropriate starting dose, while 8 mg may be used for more severe symptoms or in patients who haven't responded adequately to the lower dose. The medication should be injected into a large muscle, such as the gluteus maximus or lateral thigh. The onset of action for IM ondansetron is typically within 30 minutes, with effects lasting approximately 4-8 hours. The maximum daily dose should not exceed 24 mg in a 24-hour period. Ondansetron works by blocking serotonin (5-HT3) receptors in the chemoreceptor trigger zone and gastrointestinal tract, which helps prevent nausea and vomiting signals from reaching the brain. Common side effects include headache, constipation, and injection site reactions. For patients requiring repeated doses, consider switching to oral formulations when possible, as they are less invasive and equally effective once the patient can tolerate oral medications.
Some key points to consider when administering ondansetron include:
- The dose and frequency of administration may vary depending on the individual patient's response and the severity of their symptoms 1
- Ondansetron has been shown to be effective in reducing nausea and vomiting in various clinical settings, including postoperative nausea and vomiting 2 and acute gastroenteritis 3
- The medication is generally well-tolerated, with a low risk of serious side effects 4, 5
- As with any medication, it's essential to monitor patients for potential side effects and adjust the dose or discontinue use as needed.
In terms of specific dosing recommendations, the most recent and highest quality study 3 suggests that a single dose of ondansetron can be effective in reducing vomiting and improving outcomes in patients with acute gastroenteritis. However, the optimal dose and frequency of administration may vary depending on the individual patient's needs and response to treatment.