α2-Adrenoceptor Agonists

α₂-Adrenoceptor Agonists

α₂-Adrenoceptor agonists have received attention for their ability to produce sedation and analgesia. Their sedative properties may be related to action on ₂-re-ceptors in the locus ceruleus, and analgesia likely occurs via α ₂-receptors in the spinal cord and locus ceruleus. Agents used when sedation is desirable include oral clonidine (Catapres) and IV dexmedetomidine (Prece-dex), which has recently been approved in the United States for sedation in intensive care units. A solution of clonidine (Duraclon) is also available to provide or as a supplement for epidural analgesia. Hypnosis sufficient for surgical anesthesia is not adequate when the α₂-adrenoceptor agonists are used alone, and cardiovascu-lar side effects, including bradycardia and hypotension, limit the doses that can be used. As adjunctive drugs they significantly reduce the dose requirement for opi-oids and anesthetics during surgery.