Increased baseline sway contributes to increased losses of balance in older people following triazolam

OBJECTIVE: Although it has been stated frequently that older people are more sensitive to benzodiazepines, the relative roles of impaired baseline performance, impaired elimination, and altered responsiveness have not been defined. We evaluated postural sway and plasma triazolam concentrations after administration of placebo and triazolam 0.375 mg in both young and older healthy subjects. DESIGN: Double-blind placebo-controlled trial. PARTICIPANTS: Nine young and nine older healthy men. INTERVENTION: All subjects received triazolam 0.375 mg or placebo on different study days, which were separated by at least 48 hours. MEASUREMENTS: Postural sway, visual analog scale of drowsiness, and plasma triazolam levels. RESULTS: The older subjects swayed more during triazolam than did the younger subjects, and this resulted in an increased number of losses of balance. This difference appeared to be caused by greater baseline sway in the older subjects rather than higher concentrations or increased responsiveness. A subset of older people had a much greater number of losses of balance during triazolam than did the rest of the subjects, and these individuals could be identified from their baseline sway. CONCLUSIONS: In this study, the increase in drug effect seen in the older subjects was of similar magnitude to that of the young, but it resulted in greater postural sway after drug administration than was seen in the young. The higher postural sway and the corresponding increased instability seen in the older subjects may put these older persons at increased risk of drug-related falls. This study also suggests that it should be possible to develop techniques that will identify individuals at particular risk of drug-induced postural instability.