New antihistamine gets FDA green light

Adults and children six years of age and older who suffer with seasonal and perennial allergic rhinitis will now have another option for relief of their symptoms. Levocetirizine (Xyzal) from UCB Inc. and Sanofi-Aventis has received regulatory approval from the FDA.

"Xyzal is the active R-enantiomer of cetirizine [Zyrtec, Pfizer]," said H. William Kelly, Pharm.D., Professor Emeritus of Pediatrics at the University of New Mexico School of Medicine in Albuquerque. As such, the new antihistamine exerts its effect quickly and is long-lasting. According to the manufacturer, peak plasma con centrations of levocetirizine are achieved 0.9 hours after dosing, with activity persisting for at least 24 hours; it is dosed once daily.

Specifically, for adults and children 12 years of age and older, the recommended dose of levocetirizine is 5 mg once daily in the evening, but some patients may be adequately controlled with just 2.5 mg once a day. Children six to 11 years of age should be given 2.5 mg once daily in the evening. In this age group, the 2.5-mg dose should not be exceeded, because the systemic exposure (area under the curve) with 5 mg is about twofold that observed in adults.

Therefore, patients taking the new drug should be cautioned against engaging in hazardous occupations that require complete mental alertness and motor coordination. In fact, in placebo-controlled trials of one to six weeks' duration in adults and adolescents 12 years of age and older, somnolence was the most common adverse reaction leading to discontinuation. Somnolence occurred in 5% of patients taking 2.5 mg levocetirizine and 6% of patients taking 5 mg. In pediatric patients aged six to 12 years of age, somnolence occurred in 3% of patients taking 5 mg levocetirizine. Other common side effects included nasopharyngitis, fatigue, dry mouth, and pharyngitis in patients 12 years of age and older, and pyrexia, cough, and epistaxis in children six to 12 years old.

Levocetirizine tablets are currently marketed in over 80 countries. The drug is expected to be available in the United States during the 2007 fall allergy season. According to Kelly, levocetirizine is not a real advance over already marketed antihistamines other than offering patent protection for an old drug. According to FDA documents, Pfizer will lose its patent protection later this year on cetirizine's tablet and syrup formulations.