Terfenadine, safety and tolerance in controlled clinical trials.

alpha-[4-(1,1-Dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) is a new histamine H1-receptor antagonist. In clinical trials, terfenadine has been studied extensively in adult patients and to a limited extent in children. Based on the results of the double-blind placebo controlled studies, the incidence of CNS depression (drowsiness, sleepiness, fatigue, weakness, lack of concentration, "fuzzy"/"blurred thinking") with doses of 120 mg/day or higher of terfenadine (12.6%) was similar to that of placebo (11.4%) while that of the comparative drugs such as chlorpheniramine (12 mg/day) or clemastine (2 mg/day) in these studies ranged from 22% to 26%. The incidences of all other side effects, including other CNS effects such as headache and stimulation with terfenadine and the other antihistamines were not different from those with placebo except for dryness of the nose, mouth or throat. Dryness was reported in a greater percentage of patients given clemastine (4.6%) or chlorpheniramine (4.5%) than in those given terfenadine (2.6%), d-chlorpheniramine (2.7%) or placebo (2.2%). It is concluded that the results of controlled clinical trials with terfenadine provide further evidence of the overall safety and lack of sedative effects of this drug.