Attenuation of the hypothalamic-pituitary-adrenal axis responsivity to the Trier Social Stress Test by the benzodiazepine alprazolam

Little is known about effects of commonly used anxiolytic drugs on psychologically evoked responses of two major stress systems, the hypothalamic–pituitary–adrenal (HPA) and the sympathetic–adrenal–medullary (SAM) axis. The purpose of the present study was to assess effects of the anxiolytic alprazolam on responses of the HPA and the SAM axes to a standardized psychosocial stress protocol, the Trier Social Stress Test (TSST). Forty-six healthy, non-smoking, non-medicated males, aged between 18 and 45 years, were invited once to the laboratory and received a single oral dose of 1 mg alprazolam or placebo, respectively, 1 h prior to the TSST. The secretion of ACTH, cortisol, epinephrine, norepinephrine as well as changes in heart rate, blood pressure, and psychological states (anxiety, wakefulness, good mood, calmness) in response to the TSST were measured. Subjects pre-treated with alprazolam showed a strongly blunted response of ACTH as well as total and free cortisol to the TSST. Whereas alprazolam-treated subjects displayed significantly lower systolic blood pressure immediately before the TSST, neither the secretion of epinephrine, norepinephrine nor changes of heart rate in response to the stress test differed from placebo-treated subjects. Regarding psychological parameters, alprazolam clearly decreased subjective ratings on the questionnaire scale “wakefulness” and increased ratings on the scale “good mood”, whereas ratings on scales assessing “state anxiety” or “agitation” were not affected.

In healthy subjects, we observed a dissociation of the effects of alprazolam on the endocrine and the autonomic response to psychosocial stress. The psychological responses seemed to be masked by sedative properties of alprazolam.