Cetirizine Pediatric Dosing
For children 6 years and older, cetirizine 10 mg once daily is the recommended dose, while children 6-11 months require 0.25 mg/kg twice daily (approximately 2.5 mg per dose), and children 12 months to 5 years need 2.5 mg twice daily or 5 mg once daily. 1, 2
Age-Based Dosing Algorithm
Infants 6-11 Months
- Dose: 0.25 mg/kg twice daily (morning and evening) 2, 3
- Formulation: Use oral drops for precise weight-based dosing 4
- Mean daily dose: Approximately 4.5 mg total per day 3
- Rationale: Twice-daily dosing is necessary due to rapid oral clearance in very young children, with an elimination half-life of only 3.1 hours in this age group 5, 2
Children 12-23 Months
- Dose: 2.5-3.5 mL twice daily (morning and evening) 2
- Safety: Long-term safety established in the ETAC trial for infants 12-24 months 2
- No cardiac effects: QT prolongation was not observed compared to placebo 2
Children 2-5 Years
- Dose: 2.5 mg twice daily OR 5 mg once daily 6
- Formulation: Syrup formulation preferred for accurate dosing 7
Children 6-11 Years
- Dose: 5-10 mg once daily 1, 7
- Evidence: 10 mg once daily produces significantly greater symptom reduction than 5 mg in seasonal allergic rhinitis (mean TSS reduction 3.2 vs 2.4) 7
- For perennial allergic rhinitis: 10 mg once daily is most effective, with significant dose-response relationship (P = 0.026 for linearity) 6
Adolescents and Adults
- Dose: 10 mg once daily 8, 1
- Alternative: 5 mg once daily may be appropriate for less severe symptoms 1
Critical Dosing Adjustments
Renal Impairment
- Moderate impairment (CrCl 10-50 mL/min): Reduce dose by 50% to 5 mg once daily 2, 8
- Severe impairment (CrCl <10 mL/min): Avoid cetirizine entirely due to predominantly renal excretion 8, 4
Hepatic Impairment
- Use with caution and consider dose adjustment 2
Low Body Weight Children
- Standard age-based dosing may result in elevated mg/kg dosing and increased sedation risk in children with low body weight 2
- Consider weight-based dosing (0.25 mg/kg) rather than fixed age-based dosing in underweight children 4
Important Safety Considerations
Sedation Risk
- Incidence: 13.7% of patients experience sedation compared to 6.3% with placebo 2, 8, 4
- Higher risk: Patients 12 years and older have higher sedation rates than younger children 2
- Management: Consider evening dosing if drowsiness occurs to prevent negative effects on school performance 8
- Comparison: Sedation risk is milder than first-generation antihistamines but higher than fexofenadine, loratadine, or desloratadine 2
Timing Considerations
- Rapid onset: Cetirizine has the shortest time to maximum concentration among second-generation antihistamines 8
- Peak effect: Occurs at 2 hours in infants and toddlers 5
- Duration: Significant clinical inhibition of wheal and flare response occurs within 20 minutes and persists for 24 hours 9
- Prolonged effect in young children: 90% inhibition of wheal and 87% inhibition of flare still observed 12 hours after dosing, longer than predicted by pharmacokinetics 5
Common Pitfalls to Avoid
- Do not underdose young children: Twice-daily dosing is essential in children under 2 years due to rapid clearance 2, 5
- Do not combine with other sedating medications without considering additive CNS effects 8
- Do not use in severe renal impairment (CrCl <10 mL/min) 8, 4
- Avoid in pregnancy, especially first trimester (FDA Category B) 2, 8
Dose Escalation for Refractory Cases
- For non-responders, dose escalation up to 40 mg daily is supported for urticaria and other refractory allergic conditions (Quality of evidence III, Strength of recommendation C) 8