Dextromethorphan reduced fentanyl induced cough and stress hormones release. A randomized double blind controlled study

Background
The previous reports demonstrated variable changes in stress hormones profile when different NMDA receptor antagonists were administered and this study traced the effect of dextromethorphan premedication as an NMDA antagonist on postoperative neuroendocrine response. As dextromethorphan is a known central antitussive agent, this study also evaluated its effect on fentanyl induced cough reflex.
Methods
Sixty female patients ASA class I, undergoing posterior vaginal repair surgeries under general anesthesia were studied. Patients were allocated to one of two groups: Dextromethorphan group in which the patients received oral dextromethorphan 60 mg and Placebo group in which the patients received 20 ml of water for injection orally 60 min prior to surgery. The incidence of cough was calculated following fentanyl 2 μg/kg administration and the severity was assessed by using cough assessment scale. Stress hormones were collected before surgery and again at 1 and 12 h postoperatively and compared. The appearance of adverse reactions was reported.
Results
The incidence of reflex fentanyl cough was lower in dextromethorphan group 13% (4 patients) in comparison to placebo 36% (11 patients). Two patients developed mild and two moderate forms in the DEX group in relation to six mild, four moderate, and one severe cough form in the control group. The stress hormones were significantly higher at 1 and 12 h postoperatively in both groups in comparison to its preoperative values. However, at 1 h postoperatively, ACTH, epinephrine, and growth hormone values were significantly low in the dextromethorphan group (59.5 ± 21.7 pg/ml, 144.4 ± 11.4 pg/ml, and 3.7 ± 0.8 ng/ml, respectively) relative to the control group (72.2 ± 21.9 pg/ml, 159.6 ± 19.7 pg/ml, and 4.4 ± 1.2 ng/ml, respectively) but these changes became insignificant at 12 h.
Conclusion
Premedication with 60 mg dextromethorphan reduced the rise in stress hormones at 1 h postoperatively. Also, the use of dextromethorphan decreased the incidence and severity of fentanyl induced cough.