Neuroendocrine and monoaminergic responses to acute administration of alprazolam in normal subjects

The effect of a single dose (3 mg) of alprazolam on plasma cortisol, growth hormone (GH), prolactin, norepinephrine (NE) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) was studied in 10 healthy males. Alprazolam and placebo were administered orally in a crossover design and blood was sampled for 24 h. In comparison to placebo, alprazolam significantly reduced plasma cortisol levels and raised plasma GH levels. Prolactin levels were elevated by 100% from 2 to 8 h after alprazolam administration. The robust increase in prolactin levels is less consistent with previously reported data on traditional benzodiazepines. Plasma NE levels following alprazolam were lower than following placebo administration only at one time point, and MHPG concentrations were not affected. The lack of change in NE and MHPG levels suggests that the acute effect of alprazolam in normal subjects is not mediated via the central noradrenergic system.