Cetirizine Dosing for 18-Month-Old Toddler
For an 18-month-old toddler weighing 14kg, the appropriate dose is 2.5 mL of cetirizine 5mg/5mL syrup (delivering 2.5mg), given twice daily.
Dosing Rationale
The FDA-approved dosing for cetirizine in children under 6 years requires consultation with a physician, as the standard labeling states "ask a doctor" for this age group 1. However, evidence-based pediatric dosing has been well-established through clinical trials:
Weight-Based Dosing Approach
- The recommended dose for infants and young children is 0.25 mg/kg twice daily 2, 3
- For a 14kg toddler: 14kg × 0.25 mg/kg = 3.5 mg per dose
- With a 5mg/5mL formulation: 3.5mg ÷ 5mg × 5mL = 3.5 mL twice daily
Alternative Conservative Dosing
- Safety studies in infants 6-11 months demonstrated that the mean daily dose was 4.5mg (approximately 0.25 mg/kg twice daily) 3
- A more conservative approach for an 18-month-old would be 2.5 mL (2.5mg) twice daily, which represents 0.18 mg/kg per dose and falls within the safe range established in clinical trials 2, 3
Clinical Evidence Supporting This Dosing
- Population pharmacokinetic studies demonstrate that levocetirizine (the active enantiomer) clearance increases with body weight and age in very young children, supporting weight-based dosing 2
- The ETAC trial studied infants 12-24 months receiving cetirizine for 18 months, establishing long-term safety in this age group 4
- Twice-daily dosing is necessary in very young children due to rapid oral clearance compared to older patients 2
Important Safety Considerations
- No cardiac effects: No QT prolongation was observed in infants receiving cetirizine compared to placebo 3
- CNS effects: Cetirizine has negligible brain penetration due to its zwitterionic structure and P-glycoprotein activity, minimizing sedation risk 5
- Sleep disturbances: A trend toward fewer sleep-related disturbances was observed in cetirizine-treated infants compared to placebo 3