Desloratadine (Clarinex) causes less drowsiness and sedation than levocetirizine (Xyzal)

Desloratadine and levocetirizine are histamine H(1) receptor antagonists (antihistamines) that were launched in the UK in 2001.

Histamine structure. Image source: Wikipedia.

Exposure data were derived from dispensed prescriptions written by primary care physicians and outcome data were derived from questionnaires that were posted to prescribers at least 6 months after the date of the first prescription.

The cohorts comprised of more than 24,000 patients. The most frequently reported prescribing indication for both drugs was allergic rhinitis without asthma/wheezing (54%).

The incidence of first reports of drowsiness/sedation for levocetirizine or desloratadine was low 0.37% and 0.08%, respectively and statistically different.

Although the reporting rates of drowsiness and sedation are low for both drugs, patients prescribed levocetirizine were more likely to experience drowsiness and sedation in the first month of observation (after starting treatment) than patients prescribed desloratadine.

For patients with allergic rhinitis without asthma/wheezing, the odds of drowsiness/sedation were over six times greater in patients using levocetirizine than desloratadine.

References:

Comparison of the risk of drowsiness and sedation between levocetirizine and desloratadine: a prescription-event monitoring study in England. Layton D, Wilton L, Boshier A, Cornelius V, Harris S, Shakir SA. Drug Saf. 2006;29(10):897-909.

Comparison of the sedating effects of levocetirizine and cetirizine: no difference http://goo.gl/lGu3Q