Perennial allergic rhinitis: clinical efficacy of a new antihistamine.

Nasal itching, sneezing, and rhinorrhea are troublesome symptoms in patients with perennial allergic rhinitis. Most first-generation H1-receptor agonists achieve a 50% reduction in these symptoms, but their benefits are frequently offset by annoying anticholinergic and sedative side effects. Cetirizine is a major metabolite of hydroxyzine that has little anticholinergic activity and causes significantly less sedation. In addition, it can be given once a day. In placebo-controlled comparisons with terfendadine, both active drugs were comparably effective and significantly better than placebo in relieving sneezing, rhinorrhea, and nasal itching. In a multicenter, double-blind comparison with placebo, both cetirizine, 10 and 20 mg given once daily, were similarly effective and superior to placebo in reducing the overall symptoms of rhinitis. In another multicenter, double-blind study, cetirizine was comparable with diphenhydramine and significantly superior to placebo in reducing total symptom severity, sneezing, rhinorrhea, and ocular itching. The safety of cetirizine was demonstrated in all studies. Cetirizine tended to be less sedating than diphenhydramine.