The second generation allergy drug desloratadine (brand name Clarinex) significantly reduces both the runny nose and congestion of seasonal and persistent allergic rhinitis, a study shows.

Allergic rhinitis, more commonly known as hay fever, is a collection of symptoms (runny nose, sneezing, red itchy and watery eyes, nasal congestion) caused by an allergic reaction to something in the environment such as pollen, dust mites, animal dander, or mold. It can be problem throughout the year (persistent) or only during certain months (seasonal), depending on the individual and the allergic trigger.

While second generation allergy drugs are non-sedating -- a big problem with first generation antihistamines -- they are generally thought to be less effective in reducing nasal congestion than nasal sprays and decongestants.

In the current study, French and Swedish researchers randomly assigned 584 people with allergic rhinitis to desloratadine (5 milligrams daily) or inactive placebo. Over the 28-day trial, the allergy sufferers kept symptom diaries and answered quality-of-life questions weekly. Unlike many previous studies, the researchers included nasal congestion as a measured symptom.

According to a report in the journal Allergy, desloratadine was significantly better than placebo in reducing both the runny nose and congestion of seasonal and persistent allergic rhinitis.

Desloratadine led to significant symptom relief by the end of day three in both seasonal and persistent allergy sufferers, the study team found. The full extent of symptom relief was reached after two weeks on the drug.

At various times during the trial and at its conclusion, the group taking desloratadine felt better and slept better compared to the placebo group, the researchers report.

Previous studies have demonstrated much slower onset of action of other second generation antihistamines in persistent allergic rhinitis, but the present study emphasizes the rapid relief of nasal congestion with desloratadine in these patients, the investigators note.

Clarinex (desloratadine) is the prescription version of the over-the-counter drug Claritin (loratadine), which is available in generic form. As with loratadine, desloratadine it is taken in pill form daily.

Cost may be the biggest difference between the two drugs with desloratadine costing about twice the generic loratadine. A generic version of desloratadine will not be available until 2012 at the earliest.

Study co-author Dr. Philippe Devillier of Foch Hospital in Suresnes, France, told Reuters Health that there's no demonstrated difference in the clinical efficacy of desloratadine and loratadine but that desloratadine may pose less risk of interacting with other drugs.

The study was funded by Schering-Plough, maker of Clarinex. Four of the study's seven authors were Schering-Plough employees.

The most common allergic illness in the United States, allergic rhinitis affects about 40 million people every year resulting in 5.5 million sick days away from school or work.

In 2000, Americans spent about $9 billion for symptom relief medications.

SOURCE: Allergy, November 2009.