Cetirizine — NZ Medication Guide

📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.

What is Cetirizine?

Cetirizine is a second-generation antihistamine used for allergic rhinitis, urticaria, and other allergic conditions. This medication is funded by Pharmac and available over-the-counter at NZ pharmacies.

What is Cetirizine Used For?

Cetirizine is used for allergic rhinitis (hay fever), chronic idiopathic urticaria (hives), allergic conjunctivitis, insect bite reactions, and other IgE-mediated allergic conditions.

How Does Cetirizine Work?

Cetirizine selectively and competitively blocks peripheral H1 histamine receptors, preventing histamine-mediated symptoms: sneezing, itching, runny nose, watery eyes, and hives. As a second-generation antihistamine, it has minimal CNS penetration and causes less drowsiness than first-generation agents (diphenhydramine, chlorphenamine).

How to Take Cetirizine

Adults and children over 12 years: 10 mg once daily (morning or evening). Half-dose (5 mg once daily) may be adequate in some patients, particularly elderly or those with renal impairment. Can be taken with or without food.

Common Side Effects of Cetirizine

• Drowsiness (less than first-generation antihistamines — but can still occur, particularly at higher doses)
• Dry mouth
• Headache
• Fatigue
• Dizziness

Serious Side Effects — Seek Medical Attention

Contact your doctor or call 111 immediately if you experience any of the following:

• Severe allergic reaction (rare)
• Urinary retention (in patients with BPH — use with care)

Drug Interactions

Cetirizine may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:

• CNS depressants (alcohol — additive sedation despite lower sedative profile)
• Other anticholinergic medicines

New Zealand Prescribing Information

Cetirizine (5 mg, 10 mg tablets; 1 mg/mL syrup — Zyrtec® and generics) is funded by Pharmac and widely available OTC. It is one of the most commonly used antihistamines in NZ for hay fever and urticaria. Cetirizine may cause some drowsiness (more than loratadine, less than chlorphenamine) — a factor to consider when driving. For non-drowsy patients, loratadine 10 mg is an alternative.

Frequently Asked Questions

Is cetirizine non-drowsy?

Cetirizine causes less drowsiness than first-generation antihistamines, but it is not completely non-drowsy — particularly at 10 mg in individuals sensitive to its CNS effects. If drowsiness is problematic, loratadine (which has even less sedating potential) may be a better choice.

Can I take cetirizine every day for hay fever season?

Yes — cetirizine is safe for daily use during allergy season. It is one of the recommended first-line antihistamines for allergic rhinitis in NZ. For perennial (year-round) allergic rhinitis, long-term daily use under medical review is appropriate.

References & Further Information

The following New Zealand and international resources were used to inform this page. We encourage you to consult these authoritative sources for the most current information:

• New Zealand Formulary — Cetirizine
• BPAC NZ — Allergic Rhinitis Management
• Pharmac Funded Medicines Schedule

⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.

Reviewed by a Registered Pharmacist NZ