Cetirizine Syrup Dosing by Age
For infants 6-11 months, give 0.25 mg/kg (approximately 2.5 mL) twice daily; for children 2-5 years, give 2.5 mg once daily; for children 6-11 years, give 5-10 mg once daily; and for adolescents and adults, give 10 mg once daily. 1
Infants 6-11 Months
- Cetirizine is NOT recommended for infants under 6 months of age due to lack of safety data and specific product labeling restrictions 2
- For infants 6-11 months, the recommended dose is 0.25 mg/kg twice daily (morning and evening), which typically equals approximately 2.5 mL of syrup twice daily 3, 4
- Twice-daily dosing is necessary in this age group because infants have significantly faster oral clearance (elimination half-life of 4.91 hours) compared to adults (8.6 hours), requiring more frequent administration to maintain therapeutic levels 5
- This dosing regimen has been validated in randomized, double-blind, placebo-controlled trials showing safety comparable to placebo, with no cardiac effects or QT prolongation 4
Children 2-5 Years
- Give 2.5 mg once daily for children in this age range 1
- This represents half the adult dose and is well-established as safe and well-tolerated by the American Academy of Allergy, Asthma, and Immunology 1
- Second-generation antihistamines like cetirizine have an excellent safety profile in young children, in stark contrast to over-the-counter cough and cold medications which should be avoided below age 6 years 1
Children 6-11 Years
- Start with 5 mg once daily; may increase to 10 mg once daily if needed 6, 7
- Clinical trials demonstrate that 10 mg once daily provides significantly greater symptom reduction than 5 mg in this age group (mean total symptom score reduction of 3.2 vs 2.4), with the 10 mg dose showing statistical superiority over placebo 6, 7
- The 10 mg dose is particularly effective for itchy eyes, nose, and mouth symptoms 6
Adolescents and Adults
- Give 10 mg once daily as the standard dose 1
- This dosing provides effective 24-hour symptom control with rapid onset (within 20 minutes) and sustained effect 8
Critical Dosing Adjustments
Renal Impairment
- Moderate renal impairment (CrCl 10-50 mL/min): Reduce dose to 5 mg once daily 1, 3
- Severe renal impairment (CrCl <10 mL/min): Avoid cetirizine entirely due to predominantly renal excretion 1, 2
- Cetirizine is ineffective and not recommended for hemodialysis patients 1
Managing Sedation
- Approximately 13.7% of patients ≥12 years experience sedation versus 6.3% with placebo; the risk is lower in younger children 3
- If significant drowsiness occurs, either reduce the dose to 2.5 mg once daily or switch to a non-sedating alternative like loratadine or fexofenadine 3
- Consider evening dosing to minimize impact on school performance if mild sedation occurs 1
Common Pitfalls to Avoid
- Do not use cetirizine in infants under 6 months – consult product labeling and consider non-pharmacologic measures like allergen avoidance instead 2
- Do not combine with other sedating medications without considering additive CNS effects 1
- Avoid during pregnancy, especially first trimester (FDA Pregnancy Category B), unless clearly necessary 1, 3
- Do not assume standard age-based dosing is appropriate for low-weight children – this may result in elevated mg/kg dosing and increased sedation risk 3
Refractory Cases
- For non-responders, the British Association of Dermatologists supports dose escalation up to 40 mg daily in adults, though this exceeds licensed recommendations 1