Loratadine: a non-sedating antihistamine. Review of its effects on cognition, psychomotor performance, mood and sedation

Although equally potent at blocking the H-1 receptor, first- and second-gen eration antihistamines can be distinguished with respect to their different effects on the central nervous system (CNS). First-generation antihistamin es readily cross the blood-brain barrier leading to significant drowsiness, altered mood, reduced wakefulness, and impaired cognitive and psychomotor performance. This paper reviews of studies CNS functioning conducted with l oratadine, a second-generation H-1-receptor antagonist, at its therapeutic dose of 10 mg per day. Studies employing self-report measures, such as diar y cards, visual analogue scales, rating scales, and mood inventories have s hown that the effect of loratadine on somnolence, fatigue, and mood was com parable to those found with placebo. In studies exploring physiological ind ices of CNS functioning, such as EEG-evoked potentials, and sleep latency t ests, loratadine has been shown to be free of CNS effects. In addition, stu dies have investigated the effects of loratadine on actual driving performa nce, and on tests of cognitive and psychomotor functioning. On all of these performance measures, loratadine has been shown to have effects comparable to placebo. In contrast, diphenhydramine, a common first-generation antihi stamine, usually available without a doctor's prescription, has significant adverse effects on vigilance, divided attention, working memory and psycho motor performance. Impairment has been shown to occur even in the absence o f self-reported sleepiness.