Alpha2-agonists as analgesic agents.

It is well known that norepinephrine is involved in the control of pain by modulating pain-related responses through various pathways. alpha(2)-Adrenergic agonists have a well-established analgesic profile and, in the recent years, have found a wider application, in particular as adjunct to anesthetics and analgesics in perioperative settings. This review analyzes the alpha(2)-agonists currently in clinical use, starting from the prototype Clonidine, as well as the most promising and studied molecules. In addition, an overview of the imidazoles, imidazolines, and hydroxyethyl-thioureas derivatives published in both the open and patented literature is presented, providing chemical description and pharmacological data. Finally, the most commonly alpha(2)-agonists used in veterinary medicine are described. (c) 2008 Wiley Periodicals, Inc.