Anxiolytic Agents
Two main categories of anxiolytics are benzodiazepines and miscellaneous (eg, buspirone, zolpidem, zaleplon). Subclassification of benzodiazepines is based on speed of onset or duration of action, metabolism, and adverse effects. Benzodiazepines cross the bloodbrain barrier and bind to specific receptors on the GABAA complex; these receptors occur in many brain regions. The drugs do not bind to the same sites as does GABA but potentiate GABA action. Benzodiazepines are safer than barbiturates (largely obsolete); adverse effects include dependence, ataxia, and drowsiness. Diazepam, chlordiazepoxide, prazepam, and the prodrug clorazepate undergo hepatic metabolism to the intermediate oxazepam. Alprazolam, flurazepam, lorazepam, and triazolam directly undergo conjugation before excretion.
Zolpidem
and zaleplon resemble benzodiazepines in pharmacology but differ chemically. Buspirone
(an azapirone) acts on 5HT1A receptors. These last drugs have fewer
adverse effects and less abuse potential.
