Loratadine. A preliminary review of its pharmacodynamic properties and therapeutic efficacy.

Loratadine is a long acting antihistamine which has a high selectivity for peripheral histamine H1-receptors and lacks the central nervous system depressant effects often associated with some of the older antihistamines. Results from controlled clinical trials have shown that loratadine (usually 10mg once daily) is a well-tolerated and effective antihistamine which will be beneficial in patients with allergic rhinitis and chronic urticaria. It was found to be significantly superior to placebo, faster acting than astemizole and as effective as usual dosages of terfenadine, clemastine, mequitazine and azatadine in eliciting relief of symptoms. Importantly, loratadine is associated with a lower incidence of sedation than azatadine, clemastine, chlorpheniramine and mequitazine. Thus, loratadine, with its convenience of once daily administration, will be a useful addition to those drugs currently available for the treatment of patients with allergic diseases in whom a histamine H1-receptor antagonist is indicated. Indeed, it is likely to find a place as one of the newer 'agents of choice' in this setting.