Background: In perioperative period inhibition of N-Methyl-D-Aspartate receptor prevents
opioid-induced hyperalgesia and reduce postoperative opioid requirement after abdominal
surgery. Methadone is both a µ-opioid receptor agonist like Morphine and a
N-Methyl-D-Aspartate antagonist. Study Aim. To evaluate the efficacy of intraoperative
Ketamine and postoperative Methadone analgesia in preventing opioid-induced hyperalgesia
after abdominal surgery.