Cetirizine

H1 Antihistamine (2nd Gen)·Allergy & Anaphylaxis

Seasonal allergic rhinitis, chronic idiopathic urticaria

PBSANTIHISTAMINEZyrtec, Zilarex10 mg tabletS2+1

Dose

10 mg OD

Half-life

8 h

Sedation

MILD

Renal Adj.

DOSE RED.

Rapid Summary

Overview

Second-generation H1-receptor antagonist. Highly effective for allergic rhinitis and urticaria. 'Non-sedating', but actually the most sedating of the 2nd-gen class.

Maximum Dose

Max 20 mg/day (Standard dose 10 mg).

Clinical Focus

Preferred for intense acute urticaria as it works rapidly, but warn patients it may cause mild drowsiness.

Bottom Line

Cetirizine is a reliable second-generation antihistamine for allergic rhinitis and urticaria, but causes mild sedation in some patients despite being classified as non-sedating.

Formulation & Access

Brand Names

Zyrtec, Zilarex

Oral Routes

Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL).

Prescribing & PBS

Pharmacy Medicine (S2). PBS listed for specific chronic conditions.

Indications & Use

Primary

PBSTGA

Seasonal allergic rhinitis, chronic idiopathic urticaria.

Clinical Place

First-line antihistamine when rapid onset is required and mild sedation is acceptable or desired (e.g., nighttime itching).

Quick reference

Class & Role

H1 Antihistamine (2nd Gen) — Second-generation H1-receptor antagonist.

Route / Formulation

Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL). (Zyrtec, Zilarex)

Usual Dose & Max

PO 10 mg OD. Max 20 mg/day (Standard dose 10 mg).

Key Indication Doses

Allergic Rhinitis / Urticaria: PO 10 mg OD. Severe Urticaria: PO 10 mg BD (Off-label specialist escalation). Renal Impairment: Reduce dose to 5 mg OD if eGFR 10-30.

Best Uses

Cetirizine is a reliable second-generation antihistamine for allergic rhinitis and urticaria, but causes mild sedation in some patients despite being classified as non-sedating.

Avoid / Cautions

Severe renal impairment without dose adjustment. Pregnancy Category B2. (Loratadine is typically preferred).

Key Risks

Neurological: Drowsiness, fatigue (Occurs in ~14% of patients, highest among 2nd gen antihistamines). Gastrointestinal: Dry mouth (very minimal anticholinergic effect).

Key Interactions

Additive CNS depression if combined with alcohol or sedatives (due to slight BBB penetration).

Monitoring

Warn against driving or operating machinery until they know how the drug affects them. Check eGFR in the elderly before prescribing.

Clinical Pearl

Cetirizine is the active metabolite of hydroxyzine (a heavily sedating 1st-gen antihistamine). It crosses the blood-brain barrier just enough to cause drowsiness in 1 in 7 people. Prescribe at NOCTE to utilize this for sleep.

Access

Zyrtec, Zilarex10 mg tablet

Brand: Zyrtec, Zilarex
Formulation: Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL)

Cetirizine

H1 Antihistamine (2nd Gen)·Allergy & Anaphylaxis

Seasonal allergic rhinitis, chronic idiopathic urticaria

PBSANTIHISTAMINEZyrtec, Zilarex10 mg tabletS2+1

Dose

10 mg OD

Half-life

8 h

Sedation

MILD

Renal Adj.

DOSE RED.

Rapid Summary

Overview

Second-generation H1-receptor antagonist. Highly effective for allergic rhinitis and urticaria. 'Non-sedating', but actually the most sedating of the 2nd-gen class.

Maximum Dose

Max 20 mg/day (Standard dose 10 mg).

Clinical Focus

Preferred for intense acute urticaria as it works rapidly, but warn patients it may cause mild drowsiness.

Bottom Line

Cetirizine is a reliable second-generation antihistamine for allergic rhinitis and urticaria, but causes mild sedation in some patients despite being classified as non-sedating.

Formulation & Access

Brand Names

Zyrtec, Zilarex

Oral Routes

Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL).

Prescribing & PBS

Pharmacy Medicine (S2). PBS listed for specific chronic conditions.

Indications & Use

Primary

PBSTGA

Seasonal allergic rhinitis, chronic idiopathic urticaria.

Clinical Place

First-line antihistamine when rapid onset is required and mild sedation is acceptable or desired (e.g., nighttime itching).

Quick reference

Class & Role

H1 Antihistamine (2nd Gen) — Second-generation H1-receptor antagonist.

Route / Formulation

Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL). (Zyrtec, Zilarex)

Usual Dose & Max

PO 10 mg OD. Max 20 mg/day (Standard dose 10 mg).

Key Indication Doses

Allergic Rhinitis / Urticaria: PO 10 mg OD. Severe Urticaria: PO 10 mg BD (Off-label specialist escalation). Renal Impairment: Reduce dose to 5 mg OD if eGFR 10-30.

Best Uses

Cetirizine is a reliable second-generation antihistamine for allergic rhinitis and urticaria, but causes mild sedation in some patients despite being classified as non-sedating.

Avoid / Cautions

Severe renal impairment without dose adjustment. Pregnancy Category B2. (Loratadine is typically preferred).

Key Risks

Neurological: Drowsiness, fatigue (Occurs in ~14% of patients, highest among 2nd gen antihistamines). Gastrointestinal: Dry mouth (very minimal anticholinergic effect).

Key Interactions

Additive CNS depression if combined with alcohol or sedatives (due to slight BBB penetration).

Monitoring

Warn against driving or operating machinery until they know how the drug affects them. Check eGFR in the elderly before prescribing.

Clinical Pearl

Access

Zyrtec, Zilarex10 mg tablet

Brand: Zyrtec, Zilarex
Formulation: Tablets (10 mg), Oral liquid (1 mg/mL), Oral drops (10 mg/mL)