Products
Cetirizine is commercially available as film-coated tablets, lozenges, and drops (Zyrtec, generic). It has been approved in many countries since 1989.
Structure and properties
Cetirizine (C21H25ClN2O3, Mr = 388.9 g/mol) is a racemate consisting of –levocetirizine and -dextrocetirizine. It is present in drugs as cetirizine dihydrochloride, a white powder that is readily soluble in water. Cetirizine is a piperazine derivative and a carboxylic acid metabolite of hydroxyzine (Atarax), a 1st generation antihistamine. The -enantiomer levocetirizine is also commercially available (Xyzal, generics).
Effects
Cetirizine (ATC R06AE07) has antihistamine, antiallergic, and antiinflammatory properties. It has high selectivity for the H1 receptor and is nonanticholinergic and noncardiotoxic. Cetirizine passes the blood–brain barrier insignificantly and therefore causes less drowsiness and sleepiness than 1st-generation antihistamines; however, both adverse effects may still occur. The effect is rapid and long-lasting.
Indications
- Allergic rhinitis: hay fever, perennial allergic rhinitis.
- Allergic conjunctivitis
- Chronic idiopathic urticaria (hives).
Dosage
According to the professional information. Medicines are usually taken once a day, regardless of meals. In children, if necessary, the dose may be divided into two intakes (half a dose each) in the morning and evening.
Contraindications
- Hypersensitivity
- Terminal renal failure
- Children under 2 years
Full precautions can be found in the drug label.
Interactions
Interactions have been described with theophylline, glipizide, and ritonavir. Potentiation of the effects of alcohol has not been demonstrated; nevertheless, cetirizine should not be combined with alcohol as a precaution.
Adverse effects
Possible adverse effects include fatigue and drowsiness, headache, dizziness, agitation, indigestion, diarrhea, dry mouth, urinary retention, tachycardia, and visual disturbances.
