The effects of meclizine on motion sickness revisited

AIMS: Antihistamines make up the first line of treatments against motion‐sickness. Still, their efficacy and specific mechanism have come into question. The aim of this study was to investigate the effect of meclizine on motion‐sensitivity. METHODS: This study was carried out as a triple‐blinded randomized trial involving 12 healthy subjects who were exposed to (i) vestibular (VES), (ii) visual (VIS) and (iii) visual–vestibular (VIS+VES) stimulations in the roll plane. Subjects were divided into 2 groups by stratified randomization, receiving either meclizine or a placebo. Stimulations were carried out before, and after, drug administration, presented at 2 intensity levels of 14 and 28°/s(2). Eye movements were tracked, and torsional slow‐phase velocities, amplitudes and nystagmus beats were retrieved. Subjects initially graded for their motion‐sickness susceptibility. RESULTS: Susceptibility had no effect on intervention outcome. Despite large variations, repeated ANOVAS showed that meclizine led to a relative increase in torsional velocity compared to placebo during vestibular stimulation for both intensities: 2.36 (7.65) from −0.01 (4.17) during low intensities, and 2.61 (6.67) from −3.49 (4.76) during high. The visual–vestibular stimuli yielded a decrease during low acceleration, −0.40 (3.87) from 3.75 (5.62), but increased during high, 3.88 (6.51) from −3.88 (8.55). CONCLUSIONS: Meclizine had an inhibitory effect on eye movement reflexes for low accelerations during VIS+VES trials. This indicates that meclizine may not primarily work through sensory‐specific mechanisms, but rather on a more central level. Practically, meclizine shows promise in targeting motion‐sickness evoked by everyday activities, but its use may be counterproductive in high‐acceleration environments.