Clinical equivalence of IV paracetamol compared to IV dipyrone for postoperative analgesia after surgery for breast cancer

Objective: To assess clinical efficacy of IV paracetamol 1 g and IV dipyrone 1 g on a 24-h dosing schedule in this randomised, double-blinded study of 40 ASA I-III ( American Society of Anesthesiologists classification of physical status) patients undergoing surgery for breast cancer. Research design and methods: General anaesthesia using remifentanil and propofol was performed for surgery. The patients were randomly allocated to two groups, receiving infusions of paracetamol 1 g/100 mL ( Para Group) or of dipyrone 1 g/100 mL ( Dipy Group) 30 min before arrival in the recovery area and every 6 h up to 24 h postoperatively. All patients had unrestricted access to opioid rescue medication via an IV patient-controlled analgesia ( PCA) device. Main outcome measures: The primary variables for clinical equivalence were the differences between the mean values for pain scores at rest and pain scores on coughing over 30 h postoperatively. The equivalence margin was determined as +/- 10 mm on the visual analogue scale ( VAS). Results: Regarding pain scores at rest, the 90% CI of the mean differences between the treatment groups over 30 h postoperatively was found to be within the predefined equivalence margin [+7.5/-6.2], and the CI values for pain scores on coughing [+7.3/-9.0] were similar. The two groups did not differ in cumulative opioid rescue consumption ( Dipy-Group 14.8 +/- 17.7 mg vs. Para Group 12.1 +/- 8.8 mg, p = 0.54) nor in piritramide loading dose ( Dipy Group 0.95 +/- 2.8 mg vs. Para Group 1.3 +/- 2.8 mg, p = 0.545). Five patients in the Dipy Group experienced hypotension in contrast to none in the Para Group ( p = 0.047). There were no significant between-treatment differences for other adverse events, patient satisfaction scores ( p = 0.4) or quality of recovery scores ( p = 0.3). Conclusion: IV paracetamol 1 g is clinically equivalent to IV dipyrone 1 g for postoperative analgesia after surgery for breast cancer.