EFFECTS OF ALPRAZOLAM AND LORAZEPAM ON CATECHOLAMINERGIC AND CARDIOVASCULAR ACTIVITY DURING SUPINE REST, MENTAL LOAD AND ORTHOSTATIC CHALLENGE

Effects of oral alprazolam (0.5 and 1 mg) and lorazepam (2 mg) on symp athetic adrenomedullary activity and sedation were studied during supi ne rest, mental load (Color Word Test, CWT) and active standing (OCT), in 12 male volunteers in a randomized double-blind placebo-controlled cross-over design. Compared to placebo, alprazolam significantly incr eased subjective sedation, reduced plasma adrenaline and noradrenaline concentrations and mean blood pressure (MBP) during supine rest, and attenuated plasma adrenaline responses during the CWT and the OCT; the se effects during the CWT and OCT appeared to be dose-dependent. In co mparison with lorazepam (2 mg), alprazolam (1 mg) showed reduced MBP l evels during supine rest, whereas lorazepam showed a higher heart rate level during supine rest, a reduced plasma noradrenaline response to the OCT and a performance deterioration to the CWT There were no diffe rences between alprazolam (1 mg) and lorazepam regarding subjective se dation. Although the benzodiazepines were similar regarding their incr ease of sedation, alprazolam and lorazepam induced differential effect s on sympathetic adrenomedullary activity during rest and stress, wher eby suppression of adrenomedullary activity may be specific for alpraz olam.