Cetirizine

Second-generation antihistamines

ATC code: R06AE07 (Cetirizine)

Mechanism of action

Selective peripheral H1-receptor antagonist, second generation. Active metabolite of hydroxyzine. Minimal CNS penetration results in less sedation compared to first-generation antihistamines. Onset of action is 20-60 minutes after administration, duration up to 24 hours.

Indications

Allergic rhinitis

First line

First-line treatment for seasonal and perennial allergic rhinitis per ARIA guidelines. Reduces sneezing, rhinorrhea, and nasal/conjunctival itching. Adult dose is 10 mg once daily. Efficacy is comparable to loratadine, though cetirizine causes slightly more drowsiness.

Chronic urticaria

First line

First-line for chronic spontaneous urticaria. If the standard 10 mg dose fails to control symptoms, EAACI/GA2LEN guidelines allow up-dosing to 4-fold (40 mg daily) before stepping up to omalizumab. Tolerability of higher doses is generally good.

Itch in atopic dermatitis

Adjunct

Evidence for oral antihistamines in atopic dermatitis is limited. Systematic reviews do not confirm a meaningful impact on itch or disease course. In practice, however, cetirizine is sometimes used for severe nocturnal pruritus – its mild sedative effect may help with sleep.

Practical notes

Timing and administration

Take 10 mg once daily at any time. If drowsiness is bothersome, evening dosing is preferred. Onset of action is 20-60 minutes. For chronic urticaria, if 10 mg is insufficient, the physician may increase to 20-40 mg daily per EAACI recommendations.

Food and drinks

Food does not affect the extent of absorption but may delay it by about 1 hour. In practice this difference is not clinically significant. Alcohol potentiates the sedative effect – patients should be warned.

Safety

Contraindications

Hypersensitivity to cetirizine, hydroxyzine, or any component
Severe renal impairment (CrCl below 10 mL/min) without dose adjustment

Serious adverse effects

Anaphylaxis (very rare)
Severe cutaneous reactions (isolated reports)

Common adverse effects

Drowsiness (more common than loratadine but less than first-generation antihistamines)
Dry mouth
Headache
Fatigue

PregnancyFDA B

FDA category B. Animal studies showed no teratogenicity. Human data are limited. Considered a preferred antihistamine in pregnancy along with loratadine.

Breastfeeding

Passes into breast milk in small amounts. Per LactMed, compatible with breastfeeding at standard doses.