cetirizine

Cetirizine is a non-sedating antihistamine that works by blocking histamine (H-1) receptors in cells. It is similar to the other second-generation antihistamines loratadine (Claritin), fexofenadine (Allegra) and azelastine (Astelin).

Histamine is a chemical that is responsible for many of the signs and symptoms of allergic reactions, for example, swelling of the lining of the nose, sneezing, and itchy eyes. Histamine is released from histamine-storing cells (mast cells) and then attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cells to be "activated," releasing other chemicals that produce the effects that we associate with allergy, for example, sneezing.

Certirizine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine. Unlike the first-generation antihistamines, cetirizine and other second-generation antihistamines do not readily enter the brain from the blood, and, therefore, they cause less drowsiness. Cetirizine may cause more drowsiness than other second-generation antihistamines.

Cetirizine uses

• Seasonal allergies: Cetirizine is used for the relief of symptoms associated with seasonal allergic rhinitis due to allergens such as ragweed, grass and tree pollens in adults and children 2 years of age and older. Symptoms treated effectively include sneezing, runny nose, itchy nose and eyes, tearing, and redness of the eyes.
• Perennial allergies: Cetirizine is used for the relief of symptoms associated with perennial allergic rhinitis due to allergens such as dust mites, animal dander and molds in adults and children 6 months of age and older. Symptoms treated effectively include sneezing, runny nose, postnasal discharge, itchy nose and eyes, and tearing.
• Hives and itching: Cetirizine is used for the treatment of the uncomplicated skin manifestations of chronic hives in adults and children 6 months of age and older. It significantly reduces the occurrence, severity, and duration of hives and significantly reduces itching.

The FDA approved cetirizine in September 1996. 

Side effects that have been reported with cetirizine include:

• sleepiness (occurs in 14% of patients),
• dry mouth,
• nausea,
• headache,
• fatigue,
• jitteriness, and
• sore throat.

Other important but rare side effects include:

• allergic reactions,
• seizures,
• fainting, and
• low blood pressure

• The recommended dose is 5 to 10 mg daily depending on the severity of symptoms.

• Theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin) reduces the breakdown of cetirizine by 16% and can increase blood levels of cetirizine. Drugs that cause drowsiness may add to drowsiness resulting from cetirizine.

Cetirizine has not been adequately evaluated in pregnant women. Available evidence suggests that risk to the developing fetus is low.

Cetirizine is excreted in human breast milk.

What preparations of cetirizine are available?

• Tablets: 5 and 10 mg. Tablets (Chewable or orally disintegrating): 10 mg. Syrup: 5 mg/5 ml.

How should I keep cetirizine stored?

• Cetirizine should be stored in a dry place at 15 C to 30 C (59 F to 86 F).