Cetirizine: dose, uses, side effects and properties

Cetirizine is an H1 antihistamine that is used to treat a variety of allergic conditions. It is a metabolite of hydroxyzine with high affinity for peripheral H1 receptors. Cetirizine in addition inhibits release of histamine and of cytotoxic mediators from platelets as well as eosinophil chemotaxis during the secondary phase of the allergic response. Thus, it may benefit allergic disorders by other actions as well. It poorly penetrates the brain, yet many people report mild drowsiness and subjective somnolence.

It reaches a high and long-lasting concentration in the skin, which may explain its higher efficacy in urticaria/atopic dermatitis and once-daily dosage despite a 7–10-hour elimination t½. It is indicated in upper respiratory allergies, urticaria, atopic dermatitis, pollinosis and also used as adjuvant in seasonal asthma.

Drug class

H1 antihistamine, 2nd generation

Available preparations

cetirizine dihydrochloride

  • Tablet: 5 mg, 10 mg
  • Syrup: 5mg/5ml

Dosage

  • Adult: 5 – 10 mg daily (preferably at night)
  • Children: 2.5 – 5 mg daily (not recommended in children below 2 years)

Common uses

  • Common cold
  • Cough
  • Allergic rhinitis
  • Pruritis
  • Seasonal asthma
  • Urticaria and atopic dermatitis
  • Pollinosis

Side effects

Due to H1 antihistaminic action-

  • Sedation
  • Decreased alertness and concentration
  • Mild headedness
  • Increased appetite
  • Motor incoordination
  • Fatigue and tendency to fall asleep

Due to anticholinergic action-

  • Dryness of mouth  
  • Urinary hesitancy
  • Alteration of bowel
  • Blurring of vision

Pharmacological characteristics

Onset of action: 1-2 hours

Half-life (t1/2): 7-10 hours

Duration of action: 18-24 hours

Only 30% (approx.) metabolized by CYPs, less potential for drug interactions

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