Tramadol is a central-acting analgesic associated with nausea and vomiting. Clinical studies have demonstrated that glucocorticoids have analgesic and antiemetic effects when administered perioperatively. The aim of this study is to test the hypothesis that coadministration of tramadol and dexamethasone decreases both postoperative pain and tramadol requirement by patient-controlled analgesia (PCA). Forty female patients undergoing thyroidectomy under general anesthesia were enrolled in a double-blind randomized controlled study and allocated to receive dexamethasone 4 mg i.v. (dexamethasone group, n = 20) or saline (control group, n = 20). At 0, 1, 2, 4 and 22 h of PCA, tramadol consumption and pain were evaluated. Although pain (numerical rating scale 0–10) was significantly lower in the dexamethasone group compared to the control group (2.9 ± 1.4 vs. 3.8 ± 1.2, p = 0.02) at the beginning of PCA, tramadol demand was not significantly different. Although the results herein show a possible beneficial effect of a preoperative single low dose of dexamethasone on postoperative pain, the hypothesis that this corticosteroid decreases tramadol requirement is not supported.

Tramadol, a central analgesic acting on serotonin neurotransmission, is often co-used with ondansetron, a 5-HT₃ antagonist, for the management of postoperative pain to decrease nausea and vomiting. The aim of the study is to test the hypothesis that this drug combination raises tramadol requirement by patient-controlled analgesia (PCA). Forty patients undergoing hernioplasty or thyroidectomy were enrolled in a randomized, controlled study and allocated to receive ondansetron 4 mg i.v. (n = 20) or saline (n = 20). At 0, 1, 2, 4 and 24 h of PCA, tramadol consumption was evaluated. Tramadol consumption (mg × kg^–1 × h^–1) was higher in the ondansetron group at the 2-hour time point compared to the control group (0.24 ± 0.1 vs. 0.17 ± 0.16; p = 0.01). Our study suggests that ondansetron acutely reduces the analgesic efficacy of tramadol.