Controlled-release oxycodone is better tolerated than intravenous tramadol/metamizol for postoperative analgesia after retinal-surgery

PURPOSE: We assessed the clinical efficacy and tolerance of controlled-release oxycodone (CRO), comparing it with intravenous tramadol/metamizol combination in this prospective, randomised, double-blind study of 35 ASA physical status I-III patients undergoing retinal-surgery. METHODS: General anaesthesia using remifentanil and propofol was performed for surgery. On arrival in the recovery room patients were randomly allocated to two groups. The controlled-release oxycodone group (CRO Group) received 10 mg CRO. 12 h after the initial dose another 10 mg CRO were administered. Simultaneously with the initial CRO dose, and every 4 h up to 24 h postoperatively, the CRO Group received intravenous isotonic saline infusion. On arrival in the recovery room the tramadol/metamizol group (TM Group) received a placebo tablet, and 12 h later a second placebo. Simultaneously 100 mg tramadol combined with 1 g metamizol were administered intravenously every 4 h until 24 h postoperatively. All patients had access to intravenous opioid rescue medication. RESULTS: The AUC for quality of analgesia was significantly higher in the CRO Group than in the TM Group (p = 0.0023). Patient rated quality of analgesia significantly higher in the CRO Group than in the TM Group 8 h (p = 0.048), 16 h (p = 0.009) and 24 h (p = 0.001) postoperatively. There was no statistical difference in AUC for pain scores between groups (p = 0.205). The CRO Group experienced significantly less nausea than the TM Group (p = 0.012). Six patients in the TM Group in contrast to none in the CRO Group interrupted the study before finishing the study protocol (p = 0.022). CONCLUSIONS: We conclude that CRO administered twice in the first 24 h postoperatively is superior to intravenous tramadol/metamizol for postoperative analgesia after retinal surgery, with fewer adverse events and greater patient satisfaction.