Clinical studies of terfenadine in seasonal allergic rhinitis.

alpha-[4-(1,1-Dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) was evaluated in groups of at least 30 patients per drug for relief of symptoms of active allergic pollinosis on a double-blind basis during the pollen season for 3 successive years. Terfenadine 20 mg 3 times a day was as effective as chlorpheniramine maleate 4 mg 3 times a day. In each study chlorpheniramine consistently showed a higher incidence of sedation than placebo. None of the terfenadine dosage schedules up to 200 mg 3 times a day caused sedation significantly different from that of placebo or efficacy greater than that seen with 20 mg 3 times a day. The incidence of central nervous system stimulation in the terfenadine group was also not different from that of placebo.