To determine whether a second-generation, non-sedating antihistamine provides any advantage over a first-generation agent in an educational setting, researchers in Denver evaluated 63 8- to 10-year-olds with non-active allergic rhinitis in a parallel group, double-blind, placebo-controlled study. Twenty-one children were assigned to each of 3 groups: placebo, diphenhydramine (25 mg, twice daily), or loratadine (10 mg as morning dose and placebo as afternoon dose). There were 4 weekend study days over a 15-day period in a laboratory school setting. Medications were administered twice, 6 hours apart (7:45 am and 1:45 pm) on the first 3 study days. At the end of each day there was testing of comprehension of curriculum content from both an oral presentation (using a Total Verbal Instruction Score) and a reading exercise (using a Total Reading Recall Score). In addition, children self-reported their level of somnolence and were tested for computerized reaction time. Repeated measure analysis of variance was fitted for each response variable, adjusting for age, sex, weight and reading ability. The children who received loratadine and diphenhydramine performed on par with the placebo group in all areas measured (P values all >.10). The authors concluded that children, in contrast to adults, may not respond to the sedative effects of antihistamines.
As Bender et al note: “The findings of this investigation were unexpected.” Most previous studies had shown that sedating antihistamines do cause learning and performance impairment1–,3 and formal recommendations advocating non-sedating antihistamines have been made.1,4,5 However, other studies did not find a significant effect from chlorpheniramine on children’s school performance.6,7 This study would seem to corroborate that finding, and validate the impression that many clinicians have that the sedative effects of first-generation antihistamines are much milder in children than in adults. On the other hand, teasing out the effects of antihistamines can be difficult. It has been suggested that diphenhydramine does interfere with the learning process, not in the prevention of information acquisition, but in the way that information is used.3 The tests used in this newest study may simply have lacked the sensitivity to detect such differences. In addition, the study may not have had adequate power to detect clinically important differences between the 2 groups, especially in the area of self-reported somnolence, which was reported on a 5-point scale. In either case, an appreciation of the child’s discomfort, whether it is from the underlying allergic rhinitis or from the side effects of therapy, must guide our judgment to intervene.