Some patients require large doses of opioids to control postoperative pain, which can result in a prolonged period of poor pain control, and potentially increased side effects associated with large morphine doses. This may be due to insufficient morphine dose to that individual or acute tolerance ( 1 ). Ketamine is not just an anaesthetic agent but at lower doses is known to provide efficacious analgesia ( 2, 3 ). Ketamine has been shown to have a marked analgesic effect on high intensity nociceptive stimuli ( 4 ) as exhibited in postoperative pain. When given for opioid analgesia resistant cancer pain in bolus doses at two different concentrations it has been shown to be effective and have a morphine-sparing effect, without undue complications ( 5 ).