ABSTRACTObjective: This study was set up to evaluate the effects of desloratadine 7.5 mg daily, with and without alcohol, on sedation and psychomotor performance.Research methods: In a double-blind, placebo-controlled, four-way crossover trial, 25 adult patients were randomized to desloratadine 7.5 mg, desloratadine 7.5 mg plus alcohol, placebo, or placebo plus alcohol. Alcohol was weight adjusted to an average blood alcohol concentration of 0.1%. Assessments included the modified Romberg test, Stanford Sleepiness Scale, Digit Symbol Substitution Test, Serial Add Subtract Reaction Time Test, and the Psychomotor Vigilance Test. The primary variable was the mean score of each of the five tests averaged over the treatment period, expressed as the mean percent change from baseline.Results: Across these assessments, differences between desloratadine alone or with alcohol versus placebo alone or without alcohol, were not significant, whereas most differences between desloratadine and placebo alone versus desloratadine and placebo with alcohol were significant ( p < 0.01). Thus, with or without alcohol, desloratadine 7.5 mg does not increase sedation or impair psychomotor performance. Most adverse events (AEs) were mild-to-moderate in severity, with the most frequently reported individual AEs being headache, fatigue, nausea, vomiting, and dry mouth. The study does have potential limitations. The measures used are restricted to a particular profile of the known effects of alcohol only, and the relatively high doses of alcohol used alone demonstrate effects on psychomotor function and attention.Conclusions: A single dose of desloratadine does not potentiate alcohol-mediated CNS impairment. Desloratadine alone or in combination with alcohol was safe and well tolerated.