Patient experience moderate to severe pain after abdominal surgery. This post-operative pain can also contribute to complications such as respiratory impairment, cardiovascular events, ileus, sleep deprivation and mood disturbance. Opioid based patient-controlled analgesia (PCA) is commonly employed but opioids have the side effects such as respiratory depression, nausea and vomiting, sedation, pruritus and urinary retention. Bowel motility can also be affected. Consequently alternative or adjunct analgesic medications without these side-effects have been investigated in order to reduce opioid consumption.