Alpha-2 Adrenergic Agonists

Alpha-2 adrenoreceptor agonists are increasingly used in perioperative settings. Activation of these receptors inhibits the release of norepinephrine in a form of negative feedback loop in both central and peripheral nervous systems. Alpha-2 adrenoreceptor is a G protein-coupled receptor with three highly homologous subtypes, α-2a, α-2b, and α-2c. Alpha-2 adrenoreceptor agonists are indicated for anxiolysis, sedation, analgesia, treatment for delirium and shivering, and many other applications in perioperative medical practice. There are many alpha-2 adrenoreceptor agonists on the market, but dexmedetomidine and clonidine are the two most commonly used. Both drugs may cause withdrawal syndrome if discontinued abruptly after 2 days or longer administration. Patients on long-term clonidine therapy can continue in the perioperative period and should not stop them abruptly, rebound hypertension and tachycardia from abrupt discontinuation may occur. Both drugs have been found to lower anesthetic and analgesic requirements in the perioperative period.