Pharmacology and clinical efficacy of terfenadine, a new H1-receptor antagonist.

Terfenadine is the first of a new class of non-sedating H1 antihistamines. It differs from chlorpheniramine in its lower anticholinergic activity in rabbit salivation tests. In animal model distribution studies, the drug is not found in the brain. In most clinical studies sedation attributed to terfenadine was on the order of that observed with placebo. Clinical trials of efficacy show that at best terfenadine is slightly less effective than or as effective as chlorpheniramine.