What is the appropriate dose of ondansetron (Zofran) for a 19 kg child with nausea and vomiting?

Appropriate Ondansetron Dosing for a 19 kg Child

For a 19 kg child with nausea and vomiting, the appropriate dose of ondansetron is 0.15 mg/kg, which equals 2.85 mg (rounded to 3 mg). This dosing is based on current pediatric clinical guidelines that recommend weight-based dosing for optimal efficacy and safety 1.

Dosing Recommendations

Weight-Based Dosing

• The recommended dose for pediatric patients is 0.15 mg/kg (maximum 16 mg) 1
• For a 19 kg child: 19 kg × 0.15 mg/kg = 2.85 mg (round to 3 mg)

Administration Routes

• Oral administration: Preferred for mild-moderate vomiting in outpatient settings
• IV/IM administration: For moderate-severe vomiting or when oral intake is not tolerated

Dosing Frequency

• For acute vomiting: Single dose is often sufficient
• For persistent vomiting: May repeat every 8 hours as needed
• Maximum daily dose should not exceed 16 mg

Clinical Considerations

Efficacy

• Ondansetron effectively reduces vomiting episodes and decreases the need for IV hydration and hospitalization in pediatric patients 2
• Studies have shown that ondansetron is significantly more effective than other antiemetics like metoclopramide and chlorpromazine 2
• The combination of ondansetron with dexamethasone may improve antiemetic efficacy compared to either agent alone in certain clinical scenarios 2

Safety Considerations

• Ondansetron is generally well tolerated in children, with headache, constipation, and diarrhea being the most commonly reported adverse events 2
• Patients with congenital long QT syndrome or those taking other medications that prolong the QT interval should be monitored for QT interval prolongation 1
• Ondansetron may increase diarrhea episodes in the 48 hours following administration, particularly in gastroenteritis 1

Dose-Response Relationship

• Research has shown that within the dose range of 0.13-0.26 mg/kg, higher doses of ondansetron were not superior to lower doses, nor were they associated with increased side effects 3
• This supports the standard dosing recommendation of 0.15 mg/kg as being both effective and safe

Practical Application

For Acute Gastroenteritis

• Single dose of 3 mg orally is typically sufficient
• Ensure adequate hydration before administration
• Monitor for increased diarrhea as a potential side effect

For Chemotherapy-Induced Nausea/Vomiting

• For moderate to high emetogenic risk chemotherapy, consider combining with dexamethasone 1
• May require scheduled dosing rather than as-needed administration

For Postoperative Nausea/Vomiting

• Administer 3 mg IV approximately 30 minutes before end of surgery
• May repeat once if needed in recovery

Important Caveats

• Antiemetics are not a substitute for appropriate fluid and electrolyte therapy
• Monitor for QT prolongation in patients with cardiac risk factors
• The safety and efficacy of ondansetron have not been established in infants under 6 months of age
• Dose adjustments are not typically needed for renal impairment, but consider dose reduction in severe hepatic impairment

Remember that while ondansetron is highly effective for controlling vomiting, addressing the underlying cause of the vomiting remains essential for comprehensive management.