Loratadine, a piperidine derivative related to azatadine, is a long-acting, non-sedating antihistamine with no significant antimuscarinic activity.
Loratadine is rapidly absorbed from the gastro-intestinal tract after oral administration, peak plasma concentrations being attained in about one hour. Bioavailability is increased and time to peak plasma concentrations is delayed when administered with food. Loratadine undergoes extensive metabolism. The major metabolite, descarboethoxyloratadine (desloratadine), has potent antihistaminic activity. Reported mean elimination half-lives for Loratadine and descarboethoxyloratadine are 8.4 and 28 hours respectively. Loratadine is about 98% bound to plasma proteins; descarboethoxyloratadine is less extensively bound. Loratadine and its metabolites have been detected in the breast milk, but do not appear to cross the blood-brain barrier to a significant extent. Most of a dose is excreted equally in the urine and faeces, mainly in the form of metabolites.