Pain is the most common presenting complaint in Emergency Department (ED). Morphine is the gold standard for severe pain treatment but it has an unpleasant side effects such as nausea, vomiting and respiratory depression. In addition to its antiemetic component, promethazine has analgesic component. The objectives of this study were to determine the influence of promethazine on morphine as an analgesic as well as antiemetic to prevent adverse drug reaction in acute pain management. This was a one year prospective study, approved ethically from the Ethical Committee of Universiti Sains Malaysia. We concluded that there were no statistically and clinically significant influenced of promethazine on morphine as both analgesic and antiemetic in acute pain management.