Antihistamines

Second-Generation (Nonsedating) Antihistamines

The newer second-generation antihistamines do not contain anticholinergics, so they do not usually cause drowsiness to the extent that the first generation antihistamines do. They are sometimes referred to collectively as nonsedating antihistamines.

A major 2003 analysis reported that although Benadryl, the most common first-generation antihistamine, had a more negative effect on daily activities than the newer antihistamines, the differences were modest. Researchers in the study concluded that no clear distinction exists between the first- and second-generation antihistamines.

Brand Names. The second-generation drugs include:

• Loratadine (Claritin). Claritin is available over-the-counter and is approved for children ages 2 and older. Desloratadine (Clarinex) is similar to Claritin but stronger and longer-lasting. It is available only by prescription.
• Cetirizine (Zyrtec). Zyrtec is approved for both indoor and outdoor allergies. It is the only antihistamine to date approved for infants as young as 6 months. It is available over-the-counter.
• Fexofenadine (Allegra) is also available over-the-counter.
• Acrivastine (Semprex).
• Ebastine, norastemizole, levocetirizine, and mizolastine are other second-generation antihistamines under investigation in the U.S. and Europe. Some may prove to be useful for specific populations.

For nonprescription antihistamines, some studies suggest that cetirizine (Zyrtec) is more effective than Allegra or Claritin in improving symptoms, including those in children. However, cetirizine can cause drowsiness when taken at high doses.

Zyrtec and Claritin are approved for children younger than 5 years, although most antihistamines appear to be safe in children. Zyrtec is the only antihistamine approved for both indoor and outdoor allergies and for infants as young as 6 months. Both are available in syrup form. Studies with Zyrtec have reported fewer symptoms in children allergic to dust mites, and one study reported that infants with allergies who were given Zyrtec were much less likely to develop asthma later on than untreated infants. Claritin, at this time, is generally the preferred drug for young people, however, because it has the least negative effect on concentration and learning. Women who are pregnant or nursing should avoid these medications unless recommended by a doctor.