Quzyttir (TerSera), an IV formulation of the second-generation H₁-antihistamine cetirizine, has been approved by the FDA for treatment of acute urticaria in patients ≥6 months old. Oral formulations of cetirizine (Zyrtec, and others) have been for sale over the counter for years. Quzyttir is the first parenteral formulation of a second-generation H₁-antihistamine to become available in the US; parenteral formulations of two first-generation H₁-antihistamines, diphenhydramine (Benadryl, and others) and hydroxyzine (Vistaril, and others), have been available for many years.

Allergic rhinitis can be classified as seasonal, perennial, or episodic. It is often associated with allergic conjunctivitis, rhinosinusitis, and asthma.

H₁-ANTIHISTAMINES — Oral – Oral second-generation H₁-antihistamines are the preferred first-line treatment for relief of the itching, sneezing, and rhinorrhea that characterize mild-to-moderate allergic rhinitis. They are less effective for nasal congestion.

Omalizumab (Xolair) is a recombinant humanized monoclonal anti-IgE antibody currently approved by the FDA for treatment of moderate to severe persistent allergic asthma. It has been used off-label for treatment of allergic rhinitis and food allergies. Recently the results of a phase III clinical trial indicated that omalizumab may be effective in treating chronic urticaria as well.

The use of drugs to prevent and control symptoms of allergic disorders can be optimized when patients avoid exposure to specific allergens and/or environmental conditions that trigger or worsen their symptoms.

Cetirizine (Zyrtec, and others) and cetirizine/pseudoephedrine (Zyrtec-D) are becoming available without a prescription this month for treatment of allergic rhinitis and urticaria in adults and children. Cetirizine is the second of the second-generation H1-antihistamines to become available over the counter. Loratadine (Claritin, and others) was the first.

Cetirizine has been shown to be more effective than loratadine in suppressing histamine-induced wheals in healthy volunteers (W Carey et al. Drugs Exp Clin Res 2002; 28:243), but no well-controlled clinical trials have established that any second-generation H1-antihistamine is more effective overall than any other (M Plaut and MD Valentine. N Engl J Med 2005; 353:1934).

Cetirizine may be mildly sedating in some patients, but it is significantly less sedating than first-generation H1-antihistamines such as diphenhydramine (Benadryl, and others) or chlorpheniramine (Chlor-Trimeton, and others), which have been available without a prescription for many years. Its safety in young children is better documented than that of any other first- or second-generation H1-antihistamine (Treat Guidel Med Lett 2007; 5:71).

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Levocetirizine (Xyzal - UCB/Sanofi-aventis), the active enantiomer of the second-generation H₁-antihistamine cetirizine (Zyrtec), has been approved by the FDA for treatment of seasonal and perennial allergic rhinitis (SAR and PAR) and chronic idiopathic urticaria in adults and children 6 years of age and older. Cetirizine has been approved by the FDA for over-the-counter use and may also become available generically in the US. Levocetirizine has been available in Europe since 2001.

Allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria, anaphylaxis and asthma (reviewed in Treatment Guidelines 2005; 3:33 and not included here), are prevalent worldwide, especially in industrialized countries. Pharmacologic treatment of these disorders continues to improve in efficacy and safety. In addition to using drugs to prevent and control the symptoms of their allergic diseases, patients should also be instructed to avoid, if possible, specific allergens and/or environmental conditions that trigger or worsen their symptoms.

Allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria and anaphylaxis, along with asthma (reviewed in Treatment Guidelines 2002; 1:7 and not included here), have increased in prevalence during the past 30 years and are now epidemic worldwide, especially in industrialized countries. Many safe and effective drugs are currently available for prevention and relief of symptoms in these disorders, but pharmacological treatment alone may not be sufficient. Patients should also be instructed to avoid specific allergens or environmental conditions that trigger their symptoms. Allergen-specific immunotherapy, parenteral administration of gradually increasing doses of the allergen ("allergy shots"), has been effective in allergic rhinitis, allergic conjunctivitis and allergic asthma, and also in prevention of anaphylaxis triggered by stings from bees, yellow jackets, hornets and wasps. It has not been effective in food allergy, atopic dermatitis or urticaria.

Desloratadine (des lor at' a deen; Clarinex - Schering), an active metabolite of the H1-receptor antagonist loratadine (Claritin), has been approved by the FDA for oral treatment of allergic rhinitis and chronic urticaria in patients at least 12 years old. The patent for loratadine expires in December 2002, and generic or over-the-counter versions are expected.

Astemizole (Hismanal - Janssen), a new antihistamine, was recently marketed in the USA for treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Like terfenadine (Seldane - Medical Letter, 27:65, 1985), astemizole is claimed to be no more sedating than placebo, but the new drug offers the advantage of a once-daily dosage schedule.