Cetirizine Dosing and Administration
For adults and children 6 years and older, administer cetirizine 10 mg once daily, with dose reduction to 5 mg daily in patients with moderate renal impairment (creatinine clearance 10-20 mL/min), and avoidance in severe renal impairment (creatinine clearance <10 mL/min). 1, 2
Standard Dosing by Age
- Adults and children ≥6 years: 10 mg once daily (do not exceed one 10 mg tablet in 24 hours) 1
- Adults ≥65 years: Consult physician before use, as older adults are more sensitive to antihistamine effects requiring extra caution 1, 2
- Children <6 years: Consult physician for appropriate dosing 1
- Less severe symptoms: 5 mg daily may be appropriate for milder allergic symptoms 1
Renal Impairment Dosing
Moderate renal impairment (CrCl 10-20 mL/min): Reduce dose to 5 mg daily (half the standard dose) 2, 3
Severe renal impairment (CrCl <10 mL/min): Avoid cetirizine entirely 2, 3
Hepatic Impairment Dosing
No dose adjustment needed for hepatic impairment in patients with normal renal function 2
Timing Considerations
Evening/bedtime dosing may be advantageous if mild sedation is acceptable or desired, allowing any sedative effects to occur during sleep 2
Morning dosing with rapid onset: Cetirizine reaches peak concentration within 1 hour (fastest among second-generation antihistamines), making it useful when rapid symptom relief is needed 2
- Adjust timing to ensure highest drug levels coincide with anticipated symptom periods 2
- Duration of action is 24 hours due to 8.3-hour elimination half-life 2, 4
Dose Escalation for Refractory Cases
For inadequate response to standard dosing: Increasing cetirizine above the manufacturer's licensed recommendation (up to 40 mg daily) has become common practice when benefits outweigh risks, particularly for chronic urticaria (British Association of Dermatologists guidelines: Quality of evidence III, Strength of recommendation C) 2
- Higher doses increase sedation risk without necessarily improving efficacy for most allergic conditions 2
- This approach should be reserved for patients failing standard therapy 2
Sedation Management
Cetirizine causes mild drowsiness in 13.7% of patients compared to 6.3% with placebo, distinguishing it from completely non-sedating alternatives like fexofenadine 2, 3
If bothersome daytime sedation occurs:
- Switch to bedtime dosing 2
- Consider switching to fexofenadine (completely non-sedating) or loratadine (non-sedating at recommended doses) 2, 5
Critical Pitfalls to Avoid
Do not exceed 10 mg in 24 hours for standard therapy, as higher doses increase sedation risk without necessarily improving efficacy 2, 1
Counsel all patients about mild drowsiness potential, as cetirizine is not completely non-sedating like fexofenadine or loratadine at recommended doses 2
Patients with low body mass may reach elevated dosage levels (mg/kg basis) with standard age-based dosing, potentially developing drowsiness requiring clinical monitoring 3
Avoid in severe renal impairment (CrCl <10 mL/min) and remember to halve the dose in moderate renal impairment 2, 3
Pregnancy considerations: Cetirizine is FDA Pregnancy Category B; ideally avoid all antihistamines in pregnancy, especially first trimester, but cetirizine and loratadine have acceptable safety profiles if treatment is necessary 5, 3