A double-blind, controlled evaluation of the efficacy and adverse effect profile of sustained-release alprazolam

In a double-blind, prospective study, 40 patients diagnosed with DSM-IV generalized anxiety disorder and stabilized on alprazolam therapy were randomized to receive the same dose of either conventional or sustained-released alprazolam for two weeks, followed by the other formulation of alprazolam in an identical dose for a further two weeks. Conventional alprazolam was administered thrice daily while the sustained-release formulation was administered once-daily, in the morning. Thirty four patients completed the study. Recruitment into the study was associated with a significant decrease in all measures of illness severity; however, no efficacy differences between the two forms of alprazolam were observed. Adverse effects, specifically insomnia, were reported more with the sustained-release formulation. It is concluded that once-daily sustained-release alprazolam is as effective as the conventional form of the drug, and may be preferable because of a wide range of advantages; in this study, the higher incidence of adverse effects with the sustained-release drug was probably an artefact of the experimental design, which fostered a (nighttime) state of partial drug withdrawal.