Dextromethorphan and dexmedetomidine: New agents for the control of perioperative pain

Most traditional opioids and non-steroidal anti-inflammatory drugs that are used to control perioperative pain have substantial side effects. The number of choices in clinical use was recently increased by two promising groups of drugs: N-methyl-D-aspartate receptor antagonists and central α₂ agonists. One N-methyl-D-aspartate antagonist, dextromethorphan, blocks the generation of central pain sensation that arise from peripheral nociceptive stimuli by moderating the activity of N-methyl-D-aspartate. It pre-empts the sensation of acute pain at doses of 30-90 mg without serious side effects, while reducing the amount of analgesics required perioperatively by 50%. It is available in oral form and has a confirmed lack of effect on haemodynamics and respiration. Dexmedetomidine is a relatively new, highly selective central α₂ agonist. Its sedative, pro-anaesthetic and pro-analgesic effects at 0.5-2 μg/kg given intravenously stem mainly from its ability to blunt the central sympathetic response by as yet unknown mechanism(s) of action. It also minimises opioid-induced muscle rigidity, lessens postoperative shivering, causes minimal respiratory depression, and has haemodynamic stabilising effects.