Second-generation antihistamine (H1 antagonist) Pregnancy: Generally considered safe. Loratadine often preferred (more data).

Cetirizine

Brand names: Zirtek, Benadryl Allergy

Adult dose

Dose: 10 mg once daily

Route: Oral

Frequency: Once daily (evening if sedating; morning if non-sedating in that patient)

Max: 10 mg/day

Allergic rhinitis, urticaria, eczema: 10 mg once daily. Less sedating than chlorphenamine. Available OTC. Evening dosing preferred for overnight effect on nasal symptoms.

Paediatric dose

Route: Oral

Frequency: Once daily

Max: 10 mg/day

Concentration: 5 mg/ml

6 months–1 year: 2.5 mg once daily (limited data). 1–2 years: 2.5 mg twice daily. 2–6 years: 2.5 mg twice daily (or 5 mg once daily). 6–11 years: 5 mg once daily or 5 mg twice daily. ≥12 years: 10 mg once daily.

Dose adjustments

Renal

Reduce dose if eGFR <30: 5 mg once daily.

Hepatic

No dose adjustment required.

Clinical pearls

Second-generation antihistamine — much less sedating than chlorphenamine
Non-sedating antihistamines preferred for daytime use and work/driving
For urticaria: up to 4× standard dose licenced under specialist guidance (BSACI)
Does not cross blood-brain barrier as readily — safer for elderly (lower fall risk than first-gen)
Loratadine and fexofenadine are truly non-sedating alternatives

Contraindications

Hypersensitivity to cetirizine or hydroxyzine

Side effects

Sedation (less common than first-generation; may still occur in some individuals)
Headache
Dry mouth
Fatigue
GI upset

Interactions

CNS depressants — additive sedation
Ritonavir — may increase cetirizine levels

Monitoring

Symptom response
Sedation level

Reference: BNFc; BNF; BSACI Urticaria Guidelines; ARIA Guidelines; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways