Future directions in anxiolytic pharmacotherapy.

It seems that psychopharmacology may be well on its way toward the goal of developing new anxiolytic drug(s) that are fast acting and free from the unwanted effects associated with the traditional benzodiazepines. Several specific candidates exist, based upon rational targeting of neurotransmitter receptors shown to be linked to the neurobiology of anxiety. Thus, partial agonists at the benzodiazepine receptor, such as alpidem, abecarnil, and bretazenil, have highly promising preclinical profiles, and some useful preliminary results in clinical testing of anxiety disorder subjects. Neurosteroids are another interesting set of pharmacologic agents that target the benzodiazepine receptor, have a preclinical anxiolytic profile, and now need to be tested in clinical populations. Targeting of various serotonin (5HT) receptor subtypes is a very active area of current research for novel anxiolytic agents. 5HT3 antagonists may have an anxiolytic profile, but clinical results are still preliminary and need more validation. Of considerable interest is the idea of developing new drugs that act at 5HT1A, 5HT2A, or 5HT2C receptors. It has even been proposed that simultaneous targeting of both 5HT2A and 5HT1A receptors could result in robust anxiolytic agents that will have more immediate onset of action than currently available 5HT1A receptor acting drugs. Neuropeptide receptor agonists and antagonists with anxiolytic properties may represent one of the most striking new classes of potential anxiolytic drugs, but this is an emerging field that still requires considerably more systematic clinical testing. Nevertheless, preclinical studies as well as early clinical studies suggest that at least three neuropeptide receptors are provocative targets for novel anxiolytic agents: namely antagonists for CCK-B receptors, antagonists for CRF receptors, and agonists for neuropeptide Y receptors. Rational development of new pharmacologic agents based upon targeting receptors for those neurotransmitters that regulate the neurobiology of anxiety promises to bring forth a number of exciting therapeutic agents for the treatment of anxiety disorders in the future.