There is no denying the fact that OIH is related to central glutaminergic system and N-methyl-d-aspartate (NMDA) receptor-activation induced central sensitization. Prostaglandins can promote glutamate release from both astrocytes and spinal cord dorsal horns with subsequent activation of the NMDA receptors, and flurbiprofen axetil, as non-steroidal anti-inflammatory drugs (NSAIDs), not only functionally antagonizes the NMDA receptor activation via inhibition of prostaglandins, but also is a targeted drug which gathers at the site of inflammation, thus greatly enhances the analgesic effect. While butorphanol has both spinal analgesic and sedative functions because of predominantly central κ-receptor agonist activation, other advantages of butorphanol include few side effects, very low addiction potential, and low toxicity on account of a partial agonist-antagonist activity to μ-receptor. Moreover, antihyperalgesic activity of κ opioids at the site of inflammation has been reported in various acute pain models. The following study is carried out to evaluate whether butorphanol combined with flurbiprofen axetil can be safely and effectively applied to preventing postoperative hyperalgesia induced by remifentanil in patients undergoing lower abdominal surgery.