Dosing Recommendations for a 24kg, 10-Year-Old Boy
For this 24kg child, prescribe: Azithromycin 240mg (10mg/kg) on day 1, then 120mg (5mg/kg) daily on days 2-5; Cefixime 192mg (8mg/kg) once daily; and Paracetamol 360-480mg every 4-6 hours as needed (maximum 2400mg/24 hours).
Azithromycin Dosing
The standard pediatric regimen is 10mg/kg on day 1, followed by 5mg/kg/day on days 2-5 1, 2:
- Day 1: 240mg (10mg/kg × 24kg)
- Days 2-5: 120mg daily (5mg/kg × 24kg)
This dosing achieves sustained tissue concentrations with mean peak serum levels of 383 ng/mL and maintains therapeutic levels for 72 hours after the final dose 3. The 5-day regimen (10mg/kg day 1, then 5mg/kg days 2-5) has comparable efficacy to the 3-day regimen (10mg/kg daily × 3 days) for respiratory infections, with clinical cure rates of 96.1% versus 95.7% respectively 4.
Alternative 3-day regimen: 240mg (10mg/kg) once daily for 3 days is equally effective for most respiratory infections 4, 5.
For atypical pneumonia (Mycoplasma, Chlamydia), azithromycin is the preferred agent using this standard dosing 1.
Cefixime Dosing
The recommended dose is 8mg/kg/day, which equals 192mg daily for this 24kg child 6:
- Single daily dose: 192mg once daily, OR
- Divided dose: 96mg every 12 hours
According to FDA labeling, this can be administered as a single daily dose or divided into two doses (4mg/kg every 12 hours) 6. Using the 200mg/5mL suspension, this child would receive 5mL once daily (200mg) as the practical dose, which slightly exceeds the calculated 192mg but remains within safe limits 6.
Maximum duration: Continue for at least 10 days if treating Streptococcus pyogenes infections 6.
Paracetamol (Acetaminophen) Dosing
Standard pediatric dosing is 10-15mg/kg per dose every 4-6 hours as needed:
- Per dose: 240-360mg every 4-6 hours
- Maximum daily dose: 75mg/kg/day or 2400mg/24 hours (whichever is less)
For this 24kg child:
- Single dose range: 240-360mg
- Maximum daily: 1800mg (75mg/kg × 24kg) or 2400mg absolute maximum
- Practical dosing: 360mg every 6 hours as needed (1440mg/24 hours total)
Clinical Context and Combination Rationale
This triple combination suggests treatment for bacterial respiratory infection, likely community-acquired pneumonia or complicated upper respiratory infection:
- Azithromycin covers atypical pathogens (Mycoplasma, Chlamydia) and some typical bacteria 1
- Cefixime provides coverage for β-lactamase producing Haemophilus influenzae and other gram-negative organisms 1, 6
- Paracetamol manages fever and pain
Important caveat: For β-lactamase negative H. influenzae, amoxicillin 75-100mg/kg/day (1800-2400mg/day for this child) would be preferred over cefixime 1. If treating community-acquired pneumonia with suspected typical bacterial pathogens, high-dose amoxicillin (90mg/kg/day = 2160mg/day in 2 divided doses) is the first-line choice 1.
Administration Considerations
Azithromycin: Can be given with or without food; suspension is well-tolerated with agreeable taste 7, 8. Gastrointestinal side effects occur in approximately 9% of patients but are typically mild 8.
Cefixime: May be administered without regard to food 6. Ensure the prescription specifies concentration (200mg/5mL preferred for this weight) to avoid dosing errors 6.
Paracetamol: Administer with food if gastrointestinal upset occurs.
Common Pitfalls to Avoid
- Do not substitute cefixime tablets for suspension in otitis media, as suspension achieves higher peak blood levels 6
- Do not exceed maximum daily paracetamol dose of 75mg/kg/day to avoid hepatotoxicity
- Ensure 10-day treatment duration if Streptococcus pyogenes is suspected 1, 6
- Do not use adult maximum doses for pediatric patients; always calculate weight-based dosing 1