Dextromethorphan is, of course, a NMDA (N-methyl-D-aspartic acid) receptor antagonist that is readily available as an over-the-counter antitussive. In recent years NMDA receptor antagonists have been shown to prevent "windup" of dorsal horn neurons, thereby attenuating the hypersensitivity or secondary hyperalgesia that follows perception of a primary noxious stimulus.

For all these reasons, one might anticipate promising results from this preemptive oral therapy. Unfortunately, however, the authors of this excellent study could not show any favorable effects of dextromethorphan on pain, sedation, or analgesic requirements in these children (who also received oral midazolam, rectal acetaminophen, and intravenous morphine). The authors proffered some possible explanations for the lack of discernible effect such as suboptimal dose, inadequate follow�up interval, as well as the potential for factors other than pain to influence pain or behavioral scores in children, etc. Moreover, the authors note that in the above-mentioned study in adults undergoing tonsillectomy, the patients were given only nonsteroidal anti-inflammatory drugs for postoperative pain. Rose and colleagues, however, thought it unethical to withhold their standard regimen of intraoperative morphine and acetaminophen to determine whether dextromethorphan by itself decreased pain and analgesic consumption in children.

It must be acknowledged that dextromethorphan�s efficacy as an analgesic adjuvant has been investigated in a variety of clinical settings with decidedly mixed results. Further studies are needed to determine whether larger doses or repeated doses might offer enhanced efficacy, being mindful that behavioral disturbances, respiratory depression, and acute dystonic reactions have been described in children who ingested cough remedies containing dextromethorphan.