ABSTRACT
Opiate narcotics are indicated for sedation, analgesia, neuroleptanalgesia, anesthetic premedication, emesis, and antitussive effects. Narcotic agents used in veterinary medicine include morphine, codeine, meperidine, fentanyl, etorphine, and pentazocine. The baine is a natural opiate which is primarily a central nervous system stimulant and is of historic interest. Opiates and opioids act at stereospecific receptors in the brain, spinal cord, and other tissues. Three such receptor types have been firmly identified. Mu receptors mediate the suppression of the opioid-withdrawal syndrome, analgesia, myosis, and respiratory depression. Kappa receptors produce spinal analgesia but do not suppress the opioid withdrawal syndrome. Sigma receptors cause mydriasis, tachypnea and mania. Drugs may act at any or all of these receptors as an agonist or antagonist. Neuroleptanalgesics are used to produce basal narcosis for minor surgical procedures, as a premedication to anesthesia, and as adjuncts to local anesthesia.
