Cetirizine dosage, side effects

Cetirizine dosage, side effects:

Cetirizine is a second-generation antihistamine used to treat allergies, hay fever (allergic rhinitis), hives (urticaria), and other allergic skin conditions. It works by blocking histamine (H1 receptors), reducing allergy symptoms like sneezing, itching, watery eyes, and runny nose.

Dosage

Adults & Children (≥12 years):

Standard dose: 10 mg once daily (can be taken in the morning or evening).
For mild symptoms or sensitive individuals: 5 mg once daily.

Children (6–11 years):

Standard dose: 5–10 mg once daily (depending on severity).

Children (2–5 years):

Dose: 2.5–5 mg once daily (often as a syrup).

Elderly & Kidney/Liver Impairment:

Reduced dose may be needed (e.g., 5 mg daily or every other day).

Brand Names

Cetirizine is sold under various brand names worldwide, including:

Zyrtec (US, Canada, UK)
Zyrtec-D (with pseudoephedrine for congestion)
Cetrizet
Aller-Tec
Reactine (Canada)
Cetzine (India)
Zirtec (Europe)
Zyrin

Drug Interactions

Cetirizine has fewer interactions than first-gen antihistamines (e.g., diphenhydramine) but may interact with:

CNS depressants (alcohol, benzodiazepines, opioids) → May increase drowsiness.
Theophylline → Slightly reduces cetirizine clearance.
Ritonavir (HIV medication) → May increase cetirizine levels.
Anticholinergics (e.g., atropine) → May enhance side effects like dry mouth.

Side Effects

Common: Drowsiness (less than 1st-gen antihistamines), dry mouth, headache, dizziness.
Rare: Fatigue, nausea, diarrhea, palpitations.

Contraindications & Precautions

Avoid in severe kidney disease (dose adjustment needed).
Pregnancy (Category B) – Use only if clearly needed.
Breastfeeding – Small amounts pass into breast milk; consult a doctor.

Key Notes

Non-drowsy? Most people tolerate it well, but some experience drowsiness.
Overdose risk: Low, but may cause extreme drowsiness (seek medical help if needed).
Works in 1 hour, lasts 24 hours.