Efficacy of pre- and postoperative oral dextromethorphan for reduction of intra- and 24-hour postoperative morphine consumption for transabdominal hysterectomy.

OBJECTIVE: We studied the effect of dextromethorphan (DEX), an N-methyl-D-aspartate receptor antagonist, on analgesic consumption and pain scores after abdominal hysterectomy. We aimed to compare the analgesic effectiveness and incidence of adverse side effects of oral DEX with placebo (P).

DESIGN: This was a double-blinded, randomized, placebo-controlled study.

SETTING AND PATIENTS: One hundred patients were randomized to two groups. Group DEX was given 30-mg tablets of oral DEX with their premedication and three more times in the first 24 hours after surgery. Group P received the placebo following the same schedule. Postoperative analgesic requirements were assessed using a patient-controlled analgesia system. Pain was assessed at rest using a visual analogue scale in the post-anesthetic care unit (PACU), 6 and 24 hours after surgery.

RESULTS: Mean pain scores were significantly lower at the PACU (62.6 vs 75.7) as was the mean sum of all resting pain scores (144.5 vs 173.1). Mean morphine consumption was greatest in the DEX group (35.1 vs 33.0 mg; P < 0.05). The sedation scores, postoperative analgesic requirements, and incidence of side effects were similar between the P and DEX groups as were the mean pain scores.

CONCLUSIONS: During PACU, however, there were two differences between the DEX and placebo groups: 1) a lower pain score at PACU; and 2) a prolonged time to the first use of morphine at PACU in the DEX group as compared with the placebo group. A low-dose DEX had a weaker though still measurable effect in this clinical trial compared with trials using higher doses.