Designer benzodiazepines: an update

The benzodiazepine receptor agonists (BzRAs) a melatonin receptor agonist and a histamine antagonist have all been approved as hypnotics. Beyond their differing mechanisms of action, they have differences in pharmacokinetics, and among the BzRAs differences in receptor subtype affinity and formulations, which provides the physician with broad options for tailoring therapy to each patient's specific needs. Consistent with their specific pharmacokinetics and formulations, these Food and Drug Administration-approved hypnotics have been shown to improve sleep with no evidence of tolerance development in long-term use. In addition, emerging data indicate these drugs also improve aspects of daytime function. Their side effects are either associated with the direct sedating effects of the drugs, doses greater than clinical doses, or a combination with alcohol or other sedating drugs. Anxiolytic BzRAs, sedating antidepressants and antipsychotics have been used off-label as hypnotics. However, in the absence of information regarding their dose range for efficacy and safety, their use as hypnotics is ill-advised.