What is the recommended dosage of cetirizine (antihistamine) for pediatric patients?

Cetirizine Pediatric Dosing

For children aged 6 years and older, administer cetirizine 10 mg once daily; for children aged 2-5 years, use 5 mg once daily (or 2.5 mg twice daily); and for infants aged 6-11 months, use 0.25 mg/kg twice daily (approximately 2.5 mg total daily dose). 1, 2

Age-Based Dosing Algorithm

Infants (6-11 months)

• Dose: 0.25 mg/kg twice daily (approximately 2.5 mg total daily) 3
• Available as oral drops for precise dosing 2
• Safety documented in randomized controlled trials with mean daily dose of 4.5 mg 3
• No CNS or cardiac adverse effects observed at this dosing 3

Preschool Children (2-5 years)

• Dose: 5 mg once daily 4
• Alternative: 2.5 mg twice daily for more consistent coverage 5
• Proven effective and safe in chronic urticaria studies in this age group 4
• The 2.5 mg dose showed less efficacy than higher doses in clinical trials 5

School-Age Children (6-11 years)

• Dose: 10 mg once daily 6, 1
• The 10 mg dose provides significantly greater symptom reduction than 5 mg (mean TSS reduction 3.2 vs 2.4) 6
• 5 mg may be appropriate for less severe symptoms 1
• Consider evening dosing if drowsiness affects school performance 2, 7

Adolescents (12 years and older)

• Dose: 10 mg once daily 2, 1
• Same as adult dosing 1

Special Population Adjustments

Renal Impairment

• Moderate impairment (CrCl 10-50 mL/min): Reduce dose to 5 mg once daily 8, 2
• Severe impairment (CrCl <10 mL/min): Avoid cetirizine entirely 8, 2
• Cetirizine is predominantly renally excreted with mean half-life of 8.3 hours 2, 9

Hepatic Impairment

• No specific dose adjustment required, but use with caution 8
• Unlike some antihistamines, cetirizine is not contraindicated in hepatic disease 8

Timing and Administration Considerations

Optimal Timing

• Evening dosing preferred if sedation occurs (13.7% experience drowsiness vs 6.3% with placebo) 2, 7, 6
• Rapid onset: significant wheal and flare inhibition within 20 minutes 9
• Duration: 24-hour symptom control with once-daily dosing 9

Dose Escalation for Refractory Cases

• May increase up to 40 mg daily in non-responders under specialist supervision 2
• Higher doses (20-40 mg) increase sedative effects significantly 7
• This is off-label but supported by British Association of Dermatologists 2

Critical Safety Considerations

Sedation Risk

• Cetirizine causes more sedation than fexofenadine, loratadine, or desloratadine at standard doses 7, 10
• Pitfall: Patients with low body mass may experience excessive sedation with standard age-based dosing 10
• Monitor school performance in children; adjust timing or switch agents if impairment occurs 2, 7

Pregnancy and Lactation

• FDA Pregnancy Category B (no evidence of fetal harm, but avoid first trimester when possible) 8, 2, 10
• Ideally avoid all antihistamines during pregnancy, especially first trimester 8, 2

Drug Interactions

• Do not combine with other sedating medications without considering additive CNS effects 2
• No significant interactions with other medications documented 9
• No cardiac adverse effects or QT prolongation 3, 9

Common Clinical Pitfalls to Avoid

1. Underdosing school-age children: The 5 mg dose is less effective than 10 mg; use 10 mg unless symptoms are mild 6, 5

2. Ignoring renal function: Always check renal function before prescribing; failure to adjust dose in renal impairment leads to drug accumulation 8, 2

3. Assuming "non-sedating" means zero sedation: Cetirizine carries meaningful sedation risk (13.7%) even at standard doses 7, 10

4. Missing weight-based overdosing: Small children may receive excessive mg/kg doses with standard age-based dosing 10

5. Not counseling about timing: Evening administration prevents school performance issues if sedation occurs 2, 7