Postoperative intramuscular dextromethorphan injection provides pain relief and decreases opioid requirement after...

Narcotics are still the therapeutic mainstay for postoperative pain relief. However, many unwanted side effects are accompanied. NMDA antagonists have been demonstrated to produce analgesic and antihyperalgesic effects, moreover, to possess potentiated effect of narcotics on postoperative pain management.

To examine whether postoperative dextromethorphan (DM), an antitussive and also an NMDA antagonist, intramuscular injection (I.M.) reduced pain and analgesic requirement after modified radical mastectomy (MRM).

Sixty-one patients scheduled for MRM were included and randomly allocated into two groups. For the control group (n=31), patients received chlorpheniramine maleate (CPM, 20 mg) I.M., while in the DM group (n = 30), 40 mg DM containing 20 mg CPM (I.M.) was given at the end of surgery. Meperidine (1 mg/kg, I.M.) was prescribed for postoperative pain relief, if ask. The time to first meperidine injection, total meperidine consumption, worst pain score, bed-rest time, and meperidine-related side effects were recorded for 48 hours postoperation.

A longer time to first meperidine injection (20.3 +/- 1.4 vs 1.5 +/- 0.2 hr, p < 0.001) and lower meperidine consumption (10.7 +/- 4.0 vs 70.7 +/- 8.9 mg, p < 0.001) were observed in the DM group than the control group. The average bed rest time was significantly shorter in the DM group than in the control group (18.9 +/- 1.5 vs 23.4 +/- 1.6 hr, p < 0.001). The number of patients who required meperidine injection (6 vs 27, p < 0.005) and meperidine-related side effects were significantly lower in the DM group than in the control group (1 vs 7, p < 0.025). No difference was noted in worst VAS pain score between the DM and the study groups.

Postoperative DM I.M. injection provided an analgesic effect and reduced meperidine requirement after MRM.