Studies on performance and sleepiness with the H1-antihistamine, desloratadine

The purpose of this study was to establish whether the H1-antihistamine desloratadine (5 mg), the active metabolite of loratadine, is free of effects on performance and sleepiness.

Effects of desloratadine (5 mg) on psychomotor performance, daytime sleep latencies, subjective sleepiness, and memory were studied in nine healthy volunteers (four men, five women) between the ages of 20 and 39 yr (mean 28.2). Assessments were made 1.0 h pre-ingestion and from 0.5 to 8.0 h post-ingestion. The study was placebo-controlled and double blind with a crossover design, using promethazine (25 mg) as an active control.

Promethazine impaired tracking (3.5-5.5 h), choice reaction time (3.5-5.5 h), digit symbol substitution (3.5-5.5 h), and attention (2.0-5.5 h). There was increased objective and subjective sleepiness (2.0-5.5 h) and subjective fatigue (3.5-8.0 h). There were no changes in any of these measures with desloratadine (5 mg). With promethazine, memory was impaired from 2.0-5.0 h. Analysis failed to establish a consistent effect on memory with desloratadine, as there was a change in only one (digit memory recall reaction time) of the twelve memory test measures at only one time point (5.5 h). The change was significant with respect to placebo, but not with respect to the pre-ingestion value.

Desloratadine (5 mg) appears to be free of adverse effects on psychomotor performance, daytime sleep latencies, and subjective sleepiness, and could prove suitable for those involved in skilled activity and transportation.