It is common nowadays to give oral analgesic supplements to post-operative patients on PCA morphine. Tramadol, an analogue of codeine, is one of the choices. However, some of the patients cannot tolerate the side effects such as nausea, drowsiness, sweating, postural hypotension and dry mouth. Combination of tramadol 37.5 mg and acetaminophen 375 mg, which has been used successfully to treat post-operative pain, may improve analgesic response with better tolerability.