PREOPERATIVE DEXTROMETHORPHAN REDUCES INTRAOPERATIVE BUT NOT POSTOPERATIVE MORPHINE REQUIREMENTS AFTER LAPAROTOMY

N-methyl-D-aspartate (NMDA) antagonists combined with opioids are thou ght to be effective in the control of pain states. We evaluated morphi ne use and analgesia in 37 patients postlaparotomy. Patients received 60 mg of oral dextromethorphan or placebo the night before and again I h before surgery. Morphine was titrated intraoperatively to maintain b lood pressure and heart rate within 20% of baseline and postoperativel y via patient-controlled analgesia (PCA). The dextromethorphan and pla cebo groups were compared for morphine use intraoperatively, in recove ry, via PCA in the first 4 and 24 h, and total use over the study peri od. Pain scores at rest and on activity for the first 4 and 24 h were also compared. Intraoperatively, the dextromethorphan group required l ess morphine: 13.1 +/-:4.3 vs 17.6 +/- 6.0 mg (P = 0.012). Postoperati vely, there was no significant difference between the dextromethorphan and placebo groups for morphine use: in the recovery room 10.9 +/- 7. 7 vs 12.1 +/- 7.7 mg; the first 4 h of PCA 15.9 +/- 9.3 vs 12.7 +/- 5. 1 mg; the first 24 h of PCA 76.4 +/- 44.7 vs 61.8 +/-: 27.5 mg; or in total morphine use 100.4 +/- 49.5 vs 91.5 +/- 33.1 mg. Pain scores for the two groups were not statistically different throughout the study period. We conclude that 60 mg of oral dextromethorphan given the nigh t before and repeated an hour before surgery does not provide a postop erative morphine-sparing effect or improve analgesia after laparotomy. Implications: Patients given dextromethorphan before surgery had sign ificantly reduced intraoperative morphine requirements. However, posto perative morphine requirements were unaltered. Dextromethorphan may ne ed to be continued postoperatively to improve postoperative analgesia.