Study designs of evaluations included in the review
Randomised double-blind clinical trials (RCTs) were eligible for inclusion. Studies with less than 10 participants were excluded. The numbers of participants in the included studies ranged from 35 to 120.
Specific interventions included in the review
Studies of parenteral or oral dextromethorphan (DM) compared with placebo were eligible for inclusion. In the included studies, DM was administered either pre- or post-operatively to treat post-operative pain; surgical procedures included haemorrhoidectomy, upper abdominal surgery, radical mastectomy, laparoscopic cholectomy and total knee replacement. Parenteral doses ranged from 10 to 120 mg and oral doses (once or twice pre-operatively, or repeated doses pre- and post-operatively) from 13 to 240 mg.
Participants included in the review
Patients undergoing any type of surgery were included. Three of the included studies were conducted in children. The included studies reported the following types of surgery: abdominal surgery, haemorrhoidectomy, mastectomy, cholecystectomy, knee replacement, tonsillectomy, hysterectomy, abortion, bone-malignancy resection and lower body surgery.
Outcomes assessed in the review
The primary outcome measures included mean pain scores at rest (early 0 to 6 hours; late 6 to 24 hours), time to first analgesic request and supplemental opioid consumption in the observation period (time to first consumption and dose). Other outcomes reported in the review include opioid-related side-effects.
How were decisions on the relevance of primary studies made?
All of the authors independently assessed studies for relevance. Consensus was reached by discussion.