Cetirizine 💊
Related Subjects:
|Allergic disorders
|Urticaria
|Allergies
💊 Cetirizine is a non-sedating (second-generation) H1 antihistamine used for hay fever, allergic rhinitis and urticaria. It is available over the counter.
📖 About
- Active metabolite of hydroxyzine; long-acting, so once-daily dosing.
- Crosses the blood–brain barrier far less than older antihistamines, but some people still feel drowsy.
- Always check the BNF or local formulary for up-to-date prescribing information.
⚙️ Mode of Action
- Selective inverse agonist at peripheral H1 receptors → reduces itch, sneeze, rhinorrhoea, wheal and flare.
- Little anticholinergic activity compared with first-generation antihistamines.
🎯 Indications
- Seasonal and perennial allergic rhinitis and conjunctivitis.
- Chronic spontaneous urticaria (specialists may use up to 4× the licensed dose - unlicensed).
- Symptomatic relief of itch in allergic skin conditions.
- ⚠️ Not a treatment for anaphylaxis - adrenaline IM is the only first-line drug.
💊 Dose
| Age | Dose |
|---|
| Adult and child ≥12 years | 10 mg once daily |
| Child 6–11 years | 5 mg twice daily |
| Child 2–5 years | 2.5 mg twice daily (oral solution) |
🫘 Renal Impairment (BNF)
- eGFR 30–49: 5 mg once daily.
- eGFR 10–29: 5 mg on alternate days.
- eGFR <10: avoid.
🔄 Interactions
- Alcohol and other CNS depressants: may enhance drowsiness in susceptible people.
- Few clinically important pharmacokinetic interactions (not significantly metabolised by CYP450).
⚠️ Cautions
- Epilepsy (rare reports of seizures).
- Urinary retention or prostatic hypertrophy (mild antimuscarinic effect at high doses).
- Warn about driving if drowsiness occurs.
- Pregnancy: loratadine or cetirizine are the usual choices if an antihistamine is needed; use the lowest effective dose.
🚫 Contraindications
- Hypersensitivity to cetirizine, hydroxyzine or piperazine derivatives.
💥 Side Effects
- Common: drowsiness, fatigue, headache, dizziness, dry mouth, pharyngitis, GI upset.
- Uncommon: agitation, paraesthesia, diarrhoea, pruritus, rash.
- Rare: tachycardia, oedema, hepatitis, urinary retention, convulsions.
📚 References
