Fexofenadine (Allegra, and others) is the most recent second-generation H₁-antihistamine to become available over the counter (OTC). Cetirizine (Zyrtec, and others) and loratadine (Claritin, and others) are already available OTC. Cetirizine can be sedating in usual doses. Loratadine can be sedating in higher-than-usual doses. Fexofenadine remains nonsedating even in higher doses.

View the Comparison Table: Some Oral Drugs for Allergic Rhinitis

Fexofenadine (fex oh fen' a deen) hydrochloride (Allegra - Hoechst Marion Roussel) has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis. An active metabolite of terfenadine, fexofenadine is being heavily advertised as "nonsedating...without 'black box' warnings."

Montelukast (Singulair - Merck) is an oral cysteinyl leukotriene D₄ receptor antagonist originally marketed for treatment of asthma. It was approved by the FDA in 2003 for treatment of seasonal allergic rhinitis and recently for use in perennial allergic rhinitis in adults and children ≥ 6 months old. Intranasal corticosteroids have generally been considered the most effective drugs available for prevention and treatment of allergic rhinitis.

Trimetrexate glucuronate (Parke-Davis), an investigational drug, is now available in the USA from the National Institute of Allergy and Infectious Diseases (NIAID) for treatment of selected AIDS patients with Pneumocystis carinii pneumonia (PCP). For this indication, trimetrexate is always used concurrently with leucovorin (Wellcovorin; and others).

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.

With the coming of spring, direct-to-consumer (DTC) advertisements in newspapers, in magazines and on television are urging people with seasonal allergies to ask their doctors about one or another of the newer, non-sedating antihistamines.

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...

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.

The FDA has approved the marketing of loratadine (Claritin - Schering), a second-generation H₁-antihistamine, without a prescription. The drug was also recently approved for OTC use as Alavert (Wyeth) and other generics are expected.