What volume in milliliters of clarithromycin suspension 250 mg/5 mL should be given to a 9‑year‑old child weighing 28 kg?

Clarithromycin Dosing for a 28 kg, 9-Year-Old Child

For a 28 kg, 9-year-old child requiring clarithromycin 250 mg/5 mL suspension, give 9.3 mL (approximately 9 mL) twice daily for most respiratory tract infections. 1

Weight-Based Dose Calculation

• The standard pediatric dose of clarithromycin for respiratory tract infections is 15 mg/kg/day divided into 2 doses for 7–14 days. 1
• For a 28 kg child: 28 kg × 15 mg/kg/day = 420 mg total daily dose, divided into 210 mg per dose twice daily. 1
• Using the 250 mg/5 mL suspension (concentration = 50 mg/mL): 210 mg ÷ 50 mg/mL = 4.2 mL per dose. 1

Alternative High-Dose Regimen for Severe Infections

• For community-acquired pneumonia or when atypical pathogens (Mycoplasma pneumoniae, Chlamydia pneumoniae) are suspected in children ≥5 years, clarithromycin may be dosed at the upper end of the range. 1
• Some guidelines support dosing up to 500 mg twice daily in children weighing >40 kg or adolescents, but for a 28 kg child the standard 15 mg/kg/day regimen remains appropriate. 1
• If using a higher dose within the labeled range (up to 500 mg/day total for this weight), calculate: 28 kg × 7.5 mg/kg per dose = 210 mg per dose (4.2 mL), which matches the standard calculation above. 1

Clinical Context and Indication

• For presumed atypical pneumonia (school-age child with gradual onset, dry cough, minimal fever): clarithromycin or azithromycin is first-line therapy. 1
• For bacterial pneumonia without atypical features in a fully immunized child ≥5 years: amoxicillin 90 mg/kg/day is preferred, and a macrolide (clarithromycin) is added only if atypical pathogens cannot be excluded clinically. 1
• Clarithromycin achieves high tissue concentrations in the respiratory tract, exceeding plasma levels, which enhances efficacy against intracellular pathogens. 2, 3, 4

Treatment Duration and Monitoring

• Complete a 7- to 10-day course for most respiratory infections; some atypical pneumonias may require up to 14 days. 1
• Clinical improvement should occur within 48–72 hours; if fever persists or symptoms worsen, reevaluate for complications (e.g., parapneumonic effusion) or alternative diagnoses. 1
• Clarithromycin is well tolerated, with fewer gastrointestinal side effects than erythromycin, improving adherence. 2, 5, 6

Important Drug Interaction and Safety Considerations

• Clarithromycin inhibits cytochrome P450 3A4, leading to potential interactions with drugs such as carbamazepine, cyclosporine, digoxin, theophylline, and warfarin; monitor closely if co-administered. 4, 5
• Avoid co-administration with pimozide, cisapride, or astemizole due to risk of serious cardiac arrhythmias. 4
• Dosage adjustment is required in severe renal impairment (creatinine clearance <30 mL/min), but not needed for mild hepatic impairment or in elderly patients. 3, 4
• Food does not significantly affect clarithromycin absorption; it may be given with or without meals. 3, 5

Practical Administration Summary

Parameter	Value
Child's weight	28 kg
Standard dose	15 mg/kg/day = 420 mg/day
Per-dose amount	210 mg twice daily
Volume per dose	4.2 mL (round to 4 mL for practical dosing)
Suspension concentration	250 mg/5 mL
Frequency	Every 12 hours
Duration	7–10 days (up to 14 days for atypical pneumonia)

Administer 4 mL of clarithromycin 250 mg/5 mL suspension twice daily for this 28 kg, 9-year-old child, ensuring the full course is completed even if symptoms improve earlier. 1